Without the premise being able to be summarized in one sentence, this falls under the category of Pet Mods. Your premises must be simple, easy to understand, and concise.Pirate Crews (AKA One Piece Mons)
Premise: each mon on your team has a specific role in the "crew" based on its team slot
Slot 1: Luffy/Captain slot. this mon's Ability becomes Long Reach, also if this mon faints, you automatically lose the battle
Slot 2: Zolo/Swordsman slot. This mon's Ability becomes Sharpness, and it gains access to every move boosted by said ability
Slot 3: Nami/Navigator slot. This mon's Ability becomes Infiltrator, and it removes all Hazards from the field upon entering battle while also taking no damage from them
Slot 4: Usopp/Shooter slot. This mon's Ability becomes Mega Launcher, and it gains access to every move boosted by said Ability
Slot 5: Sanji/Cook slot. This mon's Ability becomes Well-Baked Body, and it has access to every fire-type move
Slot 6: Chopper/Doctor slot. This mon's Ability becomes Triage, and it's Healing moves can be used on any mon in your party while it is in battle, but no other mon on your team can run any Healing moves.
Potential Threats/Bans
Each slot would likely need its own bans/restrictions, as some mons may be better suited for a specific role/slot
Questions for the Community
What mons do you think would be best suited to each Pirate Crew role?
Is the auto-loss from the Captain fainting a bit too much?
This could be a pretty interesting Solo Mod tho.