Instead of charge-discharge(get charges from attack and discharge in critical attack) system there is alternative from fighter games: combo attacks. In rpg this could be done by combining skills into one attack,
e.g. create new icon->add skills(timeslot1,2,3,4)->use the icon in skill slot.
Some combos might have bonuses or drawbacks, but this also saves time for the player who uses certain skills in sequence.
Advantage:minimal tactics, customized per situation, no dependence on pre-charge attacks.