This is an interesting concept, and I think it would add a lot of depth to the game. I never really liked the fact that for example, Black Adam's trait became "win any close game for free by just dashing in" etc.
Usually the hypest things in fighting games are the ones that have tradeoffs. Getting hit with an unblockable isn't hype.. But for example, I was watching the Cafe ID tournament and Fuudo was late into a match and about to lose the game. Everyone was trying to figure out how he could pull it out, and he literally went up and did walk up Raw Ultra on a read and won the match. It was hype, and everybody was screaming "He just did it!" because they knew that if his read was wrong or his execution was off, he'd have gotten pusnished to infinity and lost the match.
However if the Ultra was unavoidable or safe/free, then there wouldn't have been any hype at all. It'd just have been another cheap/semi-brainless mechanic.
It's the same reason it's hype when somebody DP's their opponent, and then walks right up to them and DP's them again on wakeup (like Daigo at Dreamhack). It's because it's risky as hell, but the tradeoff is good.. So you're rewarded for having the balls to risk the downside in order to get the payoff.
I know Injustice is supposed to be over-the-top, but I think that in the long term, risk/reward is what has the power to keep people enjoying and playing a game for a long time.
