welp

There's no rule a character who is already Mii Costume can't be a DLC Fighter later.

At the worst case scenario, characters like Heihachi, Bomberman and Travis can't be DLC in Fighter Pass 2, but if Nintendo changes their plans and makes a Fighter Pass 3, they can, Mii Costumes from Fighter Pass 1 like Tails, Sans and Cuphead should not be considered disconfirmed.