Trust me, I've been pushing for more women in fighting games for years, but Nero & Vergil are basically inevitable in the next Versus game (V as well, to an extent). And while I can get behind your Claire idea, I'm not sure if Capcom would go for Ada over Leon. Then again, they aren't like Sakurai in terms of his main-characters-first mentality, so maybe.
I think the problem is that Capcom as a brand isn't as strong as, say, Nintendo as a brand. If the average joe saw "Capcom All-Stars" on the shelf, they may not be as inclined to get it at a glance. Perhaps it would help if it was called "Street Fighter vs. Capcom", something to capitalize on the more well-known properties.
As for your point earlier, I avoided using Capcom Fighting Jam & the like as