I’ve been working on an almost completely custom battle system just for the sake of making it. It would be an ATB at start. Almost completely custom because I’m building it from the ground up, while using a little bit of the already existing methods, just a little bit. Most of the recycled methods are those from the battleback creation and possibly, I would still be calling the damage methods and state applications from the battler classes.
Most probably, no method from BattleManager, Game_Actions and Scene_Battle would be used.
I don’t know if I’d release this to the public though, because this means that other people’s scripts that adds something to the battle scene won’t work.