Maybe the title should be something that references that the game takes place a little before Skullgirls.
Skullgirls: Serial? (Actually goes well with how they're releasing Seasons. It just sounds weird.)
Skullgirls: Smash Cut?
Skullgirls: Tour de Force? ("literally "forceful turn" (French); usually refers to a lead actor's performance that was incredibly skillful, brilliant, notable, masterful, reflecting a very high standard, and perfectly displaying the actor's ability; compare to 'stealing a scene' - the equivalent for a supporting actor role")
Just looking at terms from here: http://www.filmsite.org/filmterms19.html