So clearly the roster is a mess, but who can we mod onto the shitty characters? I'm actually kinda hoping they split the color palettes to their own sprite sheet instead of saving space so that we can have mods that just "palette swap" though, the voicelines for tag-ins are pretty specific. Regardless, I have some of my own picks.

She-Hulk into The Thing (moveset would work well)

Captain Marvel over Pheonix or Nova, but I'm not a Richard Rider fan

Obviously Thor over Beta Ray William