This game and continuity [i]already[/i] exists. Things have been established, certain parameters have been set, and the "world" the game takes place in as it stands cannot accommodate an influx of characters that would mandate a fair amount of that to be changed after the fact without people's informed consent going in.

I don't have a problem with a game wherein Western comics and Manga exist side by side but I don't see why a pre-existing game needs to change to accommodate that. If the demand for such a game exists, make that game and people will apply for it.

This shouldn't need to be said. If there's a market for this, as people seem to think there is, be confident enough to make a separate game and let it stand on its merits.