I don't know if we are all familiar with Chrono trigger but it would be amazing if we get something like their combo system.

A bit like blm/smn can do a special attack under certain instances. Same for monk/ninja/ drg or bard/ mcn , pld/drk/war or sch/ast/whm

Combined combos would be ace to have and it kinda give a fresh look into new action for all classes.