Stance as Party skill will be realy OP in my Opinion. Would not like to see that Coming. Alltought i dont see why every Class needs party skills. Some are supposed to be Supporters some are supposed to be Attakers.
Warriors don't need to have stance as a party skill, or more party skills for that matter. If you want to have party buffs, make a different class. As stated before, some jobs are supposed to be support class & some are meant to be damage. If everyone got stance, that would be super OP (aka not so good).
UHM EXCUSE ME!!! Heros have Rage and Maple warrior, Dark Knights have Hyper Body and Maple Warrior, and Paladins have uhhhhhhh........ Maple Warrior. We good.
I think it is best to not modify game mechanics like that. Also, it would probably be a pain to implement...