Complete List of Potentially Useful Grand/Parent Options for Front Runner Parent Making (currently on global + Grand Concert)
Went through all the possible inherit options to see which would be worth making into future grandparent or parent umas for Front Runners. This will cover all umas currently released and umas released in Grand Live. Rankings are my subjective opinion of their unique skill when inherited.
TLDR: Best accel parents are Seiun Sky on most tracks, NY Kitasan Black on Medium (as an add on to Seiun), OG Kitasan Black on Long, Machan on Sprint, and Pasa on certain Sprint and Mile tracks. Best mid race speed skills are Summer Maru and Valentine Bourbon. Lots of great late race inherit options, but the best ones are Fuji Kiseki (any distance) and NY TM Opera O (Medium or Long).
Acceleration
Seiun Sky - 0.2 accel upon entering a late race corner. Used on almost all tracks in PVP. Remains a highly valuable parent for years, and is arguably still pretty damn good even considering the other more flexible accels CyGames has released over the past year in JP. Overall rank: 5/5
Special Week - 0.15 current speed and 0.05 accel after overtaking in the late race. Only works if you're using a Runaway rabbit. Particularly good on umas like Daiwa Scarlet or Kitasan Black. Gives you an extra bit of accel and some current speed when overtaking your rabbit, ideally as early as possible so the accel matters. Somewhat inconsistent. Overall rank: 4/5 if you know how to set it up, 0/5 otherwise
El Condor Pasa - 0.1 accel on any track where the acceleration zone starts on/very close to the final straight. Only used for certain Sprint and Mile events. Overall rank: 5/5 on those certain Sprint and Mile tracks, 0/5 otherwise
Maruzensky - 0.2 accel on any track where the acceleration zone starts on or during the final corner. There are very few tracks where this happens, but that list of tracks includes the evergreen Tokyo 2400m. Overall rank: 5/5 on tracks where her accel has perfect timing, 0/5 otherwise
Taiki Shuttle - 0.2 accel halfway through the final corner. Decent backup accel on any track where it can activate (some Sprint and Mile tracks). While backup accels are fine, they're inherently inconsistent since Fronts tend to want to push into 1st or 2nd. Overall rank: 3/5 on the tracks where it can work, 0/5 otherwise
Christmas Oguri - 0.1 accel in the second half of the race after activating 3 recovery skills. On tracks where you can get the third recovery skill to activate right before the accel zone, this is technically a valid accel. There aren't many tracks where this can happen, though. Overall rating: 3/5 on the tracks where it can work, 0/5 otherwise
Kitasan Black - 0.1 accel on Long tracks if top 2. Has a ~70m delay on 3600m, though considering the length of the track that might be acceptable? While Kitasan herself has niche viability even outside of Long on the handful of tracks where she gets speed carryover on her unique, as an inherit it's pretty much exclusively locked to 2500m+ since it's target speed on inherit is too low. Overall rank: 5/5 for Long tracks, 0/5 otherwise
Ballroom Seiun Sky - 0.07 accel on Long tracks if top 2. Note that OG Seiun has a (delayed) activation on Arima, so this is mostly just for Kyoto 3000m/3200m. Kind of a worse Kitasan Black, but any accel is helpful considering the lack of accel options on Kyoto Long until Daiwa Wit in Mecha Umamusume. Overall rank: 4/5 for Long tracks, 0/5 otherwise
Nishino Flower - 0.2 accel halfway through the final corner or later, 3-4. Separated for clarity. More flexible window than Taiki's, but otherwise effectively the same. Can be used on Sprint and Mile tracks. Otherwise, same deal as Taiki's. Overall rank: 3/5 on the tracks where it can work, 0/5 otherwise
Aston Machan - 0.1 accel on 1200m tracks for 1st/2nd place if your uma is an overtake target. Obviously, this is very good for Sprint distances. On tracks where Seiun Sky's doesn't work, you use this and Pasa. For tracks where it does, you use Machan over Pasa. Overall rank: 5/5 on Sprint, 0/5 otherwise
New Year Kitasan Black - 0.15 current speed and 0.05 accel on a late race corner, your uma is top 3, and the track is Medium or longer. Well, it technically can activate on the Kyoto Dirt 1900m track if you're doing community tourneys I guess. It's primarily good for its current speed, which makes it relevant even to this day in JP, but it's a decent option as your second parent on Medium tracks. It's technically fine for Long too but you'd be using OG Kita's unique instead. Overall rank: 5/5 on Medium, 3/5 on Long, 0/5 otherwise
Mid Race Speed
Sakura Bakushin O - 0.15 target speed if second half of the race, top 3, and blocked from the side for 2 seconds. A solid baseline for a mid race speed skill. Helps defend or facilitate overtakes, as most mid race speed skills do. Overall rank: 4/5
Silence Suzuka - 0.15 target speed if your uma is in 1st place in the second half of the race and there's no other uma nearby. Only reliable on Runaway umas. Decent midleg option considering most midleg skills tend to require side block or have another uma nearby. You can do better though. Overall rank: 2/5
TM Opera O - 0.15 target speed on the final corner or later if there's an uma ahead of you. Only works if you're using a Runaway rabbit. Technically can be activated in either the mid OR late race, but realistically this is only really good on tracks where the accel zone starts during the final corner so you can try and get speed carryover (wholly outclassed by other options otherwise). Can be used to further assist with overtaking your rabbit or high rolling on speed carryover, but realistically there are better options for this. Overall rank: 2/5
Wedding Air Groove - 0.15 target speed if you're top 3 and attempt to overtake another uma. Can be forced with a Runaway rabbit. Overtaking in the mid leg is pretty easy, but your uma only needs to ATTEMPT to overtake, not actually succeed. A bit unreliable since it won't work if your uma is in 1st place, but you can also try to force carryover by fielding a Runaway rabbit + strong Front Runner. Overall rank: 3/5
Summer Maruzensky - 0.15 target speed if you're top 3 and have activated a recovery skill at any point in the race. Pretty easy activation condition, especially if paired with Valentine Bourbon's inherit. On some tracks you can try to gamble a specific recovery to try and get carryover on this skill, but realistically you should just treat this as a typical mid leg. Overall rank: 5/5
Christmas Biwa Hayahide - 0.15 target speed in the second half of the race if you remained in the top 5, but are not currently in 1st. Only works if you're using a Runaway rabbit. It's a decent option, but there are better pick ups that don't whiff if you're in 1st. Overall rank: 2/5
Valentine Mihono Bourbon - 0.15 target speed during a mid race corner if top 4 and there's another uma within 3 lengths of your uma. This is extremely easy to activate on most umas, especially since it works on ANY mid race corner. It tends to activate on the earliest mid race corner though. Overall rank: 5/5
Christmas Daiwa Scarlet - 0.15 target speed for base 3.6s if your uma is in the lead on a second half straight. Has a decent chance of being the shitty 0.05 version though, considering you HAVE to be in the lead AND there needs to be an uma nearby (AKA bad for Runaways typically). Too much effort, too much RNG. Overall rank: 1/5
Late Race Speed
Mejiro McQueen - 0.15 target speed on the final corner. 0.25 if it's a Long track and you have enough HP to full spurt. Also works as a mid race speed skill, depending on where the final corner is on the track. It was good before the buffs, and it's even better after. A very good skill on any track where the accel zone starts in the third corner or earlier OR on tracks where the accel zone starts in the second half or after of the final corner. Overall rank: 5/5
Mihono Bourbon - 0.15 target speed on the final straight if your uma didn't late start and is 1st-3rd. 0.25 if your uma remained in the top 2 throughout the entire race (ignoring the first 5 seconds). Pretty good provided the accel zone isn't on the final straight, though late starting is an RNG point. Particularly good for Runaways or if you can get Concentration. Decent grandparent option since Front Runners don't have many good late race skill options. Overall rank: 4/5
Biwa Hayahide - 0.15 target speed on the final corner if 1st-4th. 0.25 if your uma didn't rush. Pretty good provided the accel zone isn't on the final corner, though rushing is an RNG point. Pretty good for any Front Runner, since you should be looping Restraint into your parent sparks anyways. Decent grandparent option since Front Runners don't have many good late race skill options. Overall rank: 4/5
Anime McQueen - 0.15 target speed if top 4 on the final corner or later and there's an uma attempting to overtake you. Has a slightly longer base duration (3.6s vs 3s). Not a bad pick up all things considered, but outclassed by better options that we can pick. If you're an overtake target, you're probably screwed anyway. Overall rank: 2/5
Fuji Kiseki - 0.25 target speed 300m before the race ends if your uma was top 4 with another uma behind. So basically, literally any uma ever. Exceptionally powerful unique inherit, and arguably the best late race speed inherit Fronts can use. 300m is extremely flexible and works regardless of the race's distance. Overall rank: 5/5
New Year TM Opera O - 0.25 target speed 400m before the race ends if your uma was top 4. I'm not going to talk about the weaker version, you're going to activate 7+ skills. Mainly works on Medium and Long tracks, where it's effectively equivalent to Fuji's unique. Not much more to say than that. Overall rank: 5/5
Zenno Rob Roy - 0.15 target speed 400m before the race ends if your uma was top 4. 0.25 if your uma is 4th or better in popularity. Technically not bad, but wholly outclassed by NY Opera and Fuji. Popularity is super RNG, so it's not even a consistent max value. Overall rank: 2/5
Blaze Narita Brian - 0.15 target speed in the second half of the final corner and your uma was top 4. Unfortunately, it doesn't seem like the inherited version retains the gigantic 0.55 (or the theoretical 0.35) target speed bonus conditional. As such, it's basically a target speed variant of Taiki/Nishino unique. Still decently useful if the second half of the final corner is well after the accel zone, but you'd probably just inherit OG McQueen's unique at that point (who also has the benefit of being able to activate in the mid race too). Overall rank: 3/5
Recovery
Super Creek - 0.035 recovery at a random point in the mid race, 2-4. Only works if you're using a Runaway rabbit. Front Runners lack particularly good recovery from the inherit slot, so for 3000m/3200m events you could consider this. With that said, you could also just use 1-2 gold recovery skill(s)/Stamina SSRs and some blue Stam sparks. Overall rank: 2/5
Mejiro Palmer - 0.015 recovery and 0.05 target speed if your uma remained in the top 2 throughout the first half of the race (ignoring the first 5 seconds). This is way below rate for an inherit, but it technically exists. Could be used as a trigger for Christmas Oguri's inherit. Overall rank: 1/5
Track Specific
Ines Fujin - 0.25 target speed on a late race uphill. This could just read "on Tokyo" and it'd be the same. Good grandparent option for any Tokyo event, which is pretty frequent (of the 50 PVP events in the future so far, 9 of them are Tokyo). With that said, you could just use NY Opera O on Medium Tokyo, so you're generally only using this on Mile (4/9 of them) alongside Fuji. Overall rank: 5/5 for Tokyo, 0/5 otherwise
Commander Special Week - 0.25 target speed after activating another skill on the final corner of Nakayama in the late race. Not going to talk about the weaker form which is completely outclassed by competitor options. There are 7 Nakayama events (as of the writing of this post) where this skill matters; 2 2000m, 4 2500m, and 1 3600m (note that 2 of these are in the most recent scenario, so they haven't happened yet). It's a good option provided you're able to activate a skill on the final corner. It's also universally useful, so if you play more than just Fronts you can easily reuse her. Overall rank: 5/5 for Nakayama Medium/Long, 0/5 otherwise
Valentine Mejiro Ryan - 0.15 target speed and 0.05 accel on a downhill 60% of the way through a race if you're 2nd or worse. Only works if you're using a Runaway rabbit. As an inherit, it's only used on very specific tracks where it has speed carryover and a bit of accel. It's not a must use on those tracks but it's a decent pickup from the grandparent slot. Generally good aptitudes across the board. Overall rank: 4/5 for Hanshin 2200m, Kyoto 2000m/2200m (basically the same tracks where Dober unique works), 0/5 otherwise
Edit: Seperated Nishino Flower from Taiki because Nishino's is technically better (though for this analysis they're still roughly the same). Added Mejiro Palmer and Christmas Oguri because technically they work.