it'll likely follow the same pattern as smash brothers, where theres more characters, some more balancing, more stages, as for castlemode, i was thinking something bigger, story mode should introduce more people from the future, as well as more castlevania bosses, like the tradidtional giant bat, and frankenstien etc..
my biggest addition would be Game costumes as unlockable, where you'd unlock the characters look from a certain title, eg sotn alucard and cv3 alucard, chronicles simon and original, the movesets would remain the same when changing the looks
I fell since they can all do holy cross, richter should do Hydro storm to differate himself, also for the wip combo he should have a way to spin the whip. that or have him the boss richter controled by shaft in story mode for alucard or maria