Adding a UI to set the type on startup can be added easily.
# ----
class myPlayer(GameTypes.KX_GameObject):
def die(self):
# ... do stuff ...
self.endObject()
# make an instance
player = myPlayer(gameOb) # gameOb is made invalid now.
player.die()
# ----
One limitation (which could also be an advantage), is making the subclass instance will return that subclass everywhere, you cant have 2 different subclasses of the same BGE data at once.