I'd like to see RVD, however can't think of a logical way to include him in the current MEM vs Originals storyline. RVD as a heel would be a tough one to pull off, and he certainly doesn't fit in with the MEM. Possibly as a mentor/leader of the originals, but that would effectively throw Joe and AJ into the back burner, because they have no chance when it comes to out-drawing the whole f'n show.
When it comes to Warrior, I got this for you:
http://www.youtube.com/watch?v=St17XgHfCIU
Having him come back to draw Sting out of the MEM would be an epic mistake. The guy just screams "change the channel" whenever he has something to say, and his ego is comparable to Hogan's. Unless he's had some sort of gimmick change in the past few years that I'm not aware of, I doubt anyone wants to see him in the main event.
Personally, I think the roster is fine as it is, if anything they need to make a few cuts. If anyone should be brought in, it would have to be to beef up the Knockouts division, as their talent pool has become rather thin.