You had me at roguelike. I would make it so you have a starting floor where you grab a few starting actions from a random selection out of existing job actions and then you can find further actions to augment your rotation from the all job actions and lost actions in the game. Whenever you gain a certain gauge increasing job action you also unlock that gauge for use. Combo actions unlock a combo for you to fill similar to how the game Remember Me let you slot in individual actions into combo strings.

My goal would be to create a system similar to the game Spell Disk where you have to create your own synergies/builds/rotation.