Yo, it's kool idea.But only for bosses and sub-bosses.

Don't you mean like the "Aggressor" from Trilogy?

MUFFINS!

huh ive never played trilogy

Well, I played trilogy a few years ago then had the game stolen from me ,but I actually remember it quite clearly(and no I was not attacked or anything for the game).
The aggressor bar would fill up when you do some combos and stuff like that then your character would start having all these blur effects and stuff added to him.I think that the character's attacks would get a little bit more stronger..Your idea by the way sounds pretty good and could be used ,but it would depend on the fighting engine that they are going to put in MK8.

Your idea sounds to me more like from 'Godzilla:Save the Earth'.You gather some circle thing that gives you rage and you do one powerful attack.