Just a random idea that popped into my head that could be useful in ABS and TBS systems. Anyone who's played Final Fantasy Tactics is aware of the Mediator (Orator in War of the Lions) class, which has a unique skill to persuade a creature or non-boss enemy to join your party as a "guest" until the end of battle, where if the creature has survived, you are given the option to add them to your party. Now, here's the thing, I know that making it so that they join your party is not an easy feat, but how about adding this little twist: The creature that joins is added as a "pet", whos skills and stats can be augmented through NPCs, Items, etc., and the creature can even evolve.
Just another random script idea from GAX72