01/04/2016 (Mon) 00:31:17
Well for overall design, here's what I've come up with so far:
Each girl has their own set of passive traits and active abilities. As they level up individually, they unlock new traits and abilities unique to them.
There would be a "Party Level" independent from character levels that always obtains experience from fights. As the party level rises, the stats of all your girls go up, regardless of whether or not they were in combat. This is so your party members will never be so underpowered that you would have to go back to a low-level zone to grind them.
Equipment is universal. Instead of buying steel swords for each party member, you would instead unlock steel swords and allow anyone capable of equipping one to do so. There could be unique equipment that can only be used by one party member at a time, but not for mundane equipment. Managing equipment for that many monster girls would be insane.
There would be special equipment called "charms" that aren't universal and can be carried by any character, each character able have have three at a time. Charms give benefits and changes to the wielder and there are a bunch of different ones with abilities that go well with certain girls. This is where the actual character customizations takes place. It's simple, but allows for a lot of interesting variety depending on how you structure your party.