Had a lightbulb moment for a possible renata ult adjustment
It would suck if Renata ulti did damage, because if you were trying to berserk an important enemy ADC and then they died, they wouldn't deal damage.
But wait, that also applies to your allies' damage. That sucks too. It's important to kill the enemy Yi, but you need that Yi to be alive to deal damage to his own team.
I present to you: W revive, but applied to enemies. If a berserked enemy dies while under the effect of Renata's ult, they will be revived with a gray health bar that ticks down over the remaining duration of the ultimate. (Getting kills doesn't turn this into a true revive.) The dead enemy will be lower on the berserk priority list than alive enemies, so they'll only hit a gray health enemy if there's no enemy champions left alive to hit.
This allows a good renata ultimate to apply its benefits more consistently even in cases where you have one full health enemy and one low health enemy, taking some of the randomness out of the ultimate. It will also reduce the instances of those highly unsatisfying renata ultis where you get a massive 5 man clustered ulti and the enemy ADC dies right away so nobody else dies and you potentially even lose the fight because of it.
I'd also accept it giving them all Trynda ult and then dealing a pop of damage at the end, like a Kindred ult in reverse. But I think that would be off-brand for a support since you would end up claiming every kill that happens during any ult.