Most definitely. Gravity pull+Gravity pull=BLACK HOLE (oh wait....) I like the possibilities, but we should be careful not to screw up decks that rely on using multiple buffs on one creature (rage potions on an archangel, for example). For buffs that don't usually stack, such as gravity pulls, adrenalines, and momentums, there could be some sort of neat debuff plus superpower (i.e.: 2 adrenalines make him attack with his final attack another 2-3 times before dying), and for buffs that usually stack, like blessings, there could be some sort of mostly buff but slight debuff.
Love the concept.