Need help with homebrew concept
Hi all! I’m new to being a DM and I have new players that love One Piece so I’ve decided to give them what they want. Okay so the title of this campaign is called “One King,” (working title) the plot is the One Piece has been found and the newly claimed Pirate King has issued an open invitation to anyone who dares challenge him to take the title of “Pirate King.” All standard dnd components like magic, magical items, creatures, come from various Devil fruit users over the decades; one of these Devil fruit users had the power to change people into animal human hybrids and created a bunch of new races in the world that regular humans have certain feelings about (some towns/island people love, tolerate, or hate these hybrids). The players start on their home island where they have been preparing for their quest to become the new Pirate King. they get to decide if they get a Devil fruit power with the disadvantage of not being able to touch salt water again (if they’re in the salt water every roll they make is halved, they’re prone, their movement goes to zero, enemies have advantage on attacks and the character has a major disadvantage on all rolls, 3 rolls with the smallest number being the outcome instead of 2 rolls). The devil fruit powers I have ideas of are flame, ice, water, lightning, rock, wind, metal, smoke, rot, rubber, nature, beast(1 animal shape), animal (all animal transformation), explosion, magic (basically wizard?). If players want a devil fruit they roll a die and get the power that’s coordinated with the number, and the power starts off weak and gets stronger with each level up. Depending on the Devil fruit power, attacks based off of physical damage has a chance to miss with each increase in level will increase the miss chance. The Rot fruit (and a randomized second fruit) goes to the BBEG, Dread Pirate Hoark who was sick of his Valrosians (walrus folk) being taken advantage of and steals a ship for his crew and plans on taking the title of Pirate king for himself. The crew purchase a special ship from the only vendor who will do business with them in town named Scam Likely. This ship is small with the cabin only being about 10 feet by 10 feet, however when going into the cabin it’s 15 feet by 10 feet. This ship ate a space fruit and can level up through sea battle (this will increase space on the entire boat, later give weapons and upgrades to the ship itself). The first couple of sessions would be at the home island to get them comfortable with the new rules. Have I gone insane by making this my first campaign AND a home brew? Yes, but I (and my players) love the idea and I want help from experts making this playable. I have an idea of how to do questlines on land but need help with water traveling, battles, and encounters. Any and all advice will be much appreciated, and if y’all have any questions I’ll answer them to the best of my ability