I actually don't mind this; it's nothing worse then say a horribly outlandish and stupid custom character you could create in SC3.
As long as Namco doesn't make any attempts to merge them into the story. You'd think it would be obvious that they wouldn't but fighting games are perhaps the most insane things of all time when it comes to story. So I wouldn't put it past them to do something as hilariously retarded as that.
I hope when Vader loses a match he goes "NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOO!!!"