I'm not usually the type to speak up multiple times about something like this, but I truly think I have a point to make. I know several people who have extensively tried to make use of center stage assist, and none of them have stuck with it (including myself). I think it's an assist that seems good in theory, but almost never in practice.
Simply selecting center stage (or a taunt, some of these points apply to those too) cripples you from character select, because you're stuck with an assist that only does something in very specific situations, is possibly the most useless alpha counter in the game, and also possibly the most high-risk assist to call in neutral;
The opponent can react to the Squigly assist showing up and then you're stuck with a useless assist waiting to get hit while the opponent can pressure you with his own assists or alpha counter into happy birthday super the moment you try to put them in blockstun.
The amount of matchups where picking center stage actually provides a justifiable net worth seems to be very few to me, maybe something like duo painwheel vs solo peacock? Most times I've used it or seen it used, it seems like a seldom callable gimmick waiting to backfire.
Is this even a concern? If they got their midstage double-snap, they would have no need for an assist extension anyway, short of the rare situation of needing just one more move to fill that last pixel of meter.
Getting to do midstage corner combos and then call another assist would certainly be good, but maybe that's the kind of good it would take for anyone to actually consider sticking with center stage after trying it.