Shade
Monster Junkie
It would be more complicated to type out, easier to use and keep track of.
OK, here's a compromise: make one statblock. But, let's state that it has 2 distinct forms, maybe an alternate form type ability. So it has some separate SAs and SQs in each form. I just don't like giving it both a slam and swarm attack at the same time. That doesn't make much sense to me; if it's solid enough to slam, it's not incoherent enough to swarm you the way we normally think of it.
Good idea. I favor this approach.