Maybe it's just optimism, but I don't see this as too much of a blow to Phoenix's chances (or any Capcom character really). Like others have said, this seems more like the elimination of competition (and fierce ones at that!)
It's not like a Capcom Mii pack has to dump a bunch of Capcom costumes, right? The closest things to something like this happening are the Mii waves of Joker (Sonic costumes), Terry (SamSho, KOF, and Art of Fighting costumes), Min Min (Splatoon costumes), and Sephiroth (Geno). Joker and Min Min's waves had costumes of already represented franchises, while Terry's wave is special because SNK has a large habit of making crossovers of their franchises. I can't really argue with Geno, but it was one costume instead of multiple. Since the most Mii costumes in one pack has been 6, it makes sense to spread some Capcom costumes along the Fighters Pass, especially because of how many good Capcom franchises there are.
I suppose you could argue that Capcom is similar to SNK in that regard, but SNK is huge on it compared to Capcom. Capcom also tends to do crossovers with other companies instead of internally.