Restricting it to just Mario characters doesn't make as much sense to me, though. A group of All-Stars that's just a bit more "street" (and I mean that in a vague sense), like say Mario, Link, Samus (sans most of her armor, probably? It'd be fun to see the lady under the battle plating still doing what she does best), and Fox McCloud, might fare better.
I mean, I like Peach, but if that corner logo is depicting some or all of the Mario characters included, I don't think she'll be a very popular pick, particularly for a game like this. Heck, Miyamoto hates the idea of Peach not being a damsel in distress anyway (I really don't think he liked what HAL did with her in Melee), I'm surprised it's OK for her to rough it up in a game of football, unless she's just going to watch from the sidelines and wave stupidly or something. (Not putting down Peach, but the way Nintendo insists she be depicted lately, like she's on a permanent dose of Valium.)