IMO Marvel games are always going to be "broken" lol. Is this glitch game breaking? At first I said no, doesn't seem practical. Waste of meter. But then I thought about it. It's kind of a double edged sword. You do force a happy B-day situation on the opponent. But the team with 2 characters can also abuse the glitch too. Having "kitty Kat helper" super permanently is abusive. Also potential for unblockable set ups.
I do see this as kind of game breaking at the highest level of play. I believe the FGC is smart enough and good enough to find ways to abuse it. That's why I think they banned it from evo.
For the casual players, I don't see it as game breaking. Chances of seeing it online is slim. Its just way too situational to pull off. Its already hard enough to pull off a 1 framer online with the lag.