The reason I suggested an ability that's effect would toggle pending your stance is because the coding is already in the game (ACN/SMN/SCH). I was thinking along the lines of XI's steps for this. If you're in coeurl form and say use Animated Flourish (30sec recast or so?) then the monster is inflicted with a ~10-15sec -DEF debuff, if Raptor a -EVA debuff, or Opo-opo a -ACC debuff or something. This way it always is benefiting the party to make up for the lack of greased lightning (while still retaining the enmity grab).
As for auras, I don't see them working. One attack will require a certain stance while giving another stance. This means your auras would last for about 3 seconds or so.