When in Attack Stance, if the player uses up all their MP while in Support Stance, then their MP will restore itself bit by bit (around Regen's HP restoration speed) so long as they stay in Attack Stance and vise versa with Support Stance. The stance switch ability would have a longer recast timer than Cleric Stance, so players wouldn't be able to gain a ridiculously high advantage in battles and abuse the ability, but be long enough to where they can gain a reasonable advantage; especially during Fates, Duties etc... Where players need to do a certain amount of damage to an emeny or any of their supports before getting hit with either an instant wipe or stacked with tons of status effects and or debuffs.