I actually think they could do Billups and Tay straight up without Mcdyess involved. Here is the thing, I believe they want Rodney Stuckey inserted into the starting lineup as a point guard. Billups brings the most value, and if Detroit were to trade Rasheed, they would have to be trading for a big man. Since no team is going to trade their best young big man for Rasheed, their best bet is trading for a SF.
Possible SF's:
Josh Smith
Tracy Mcgrady
Carmelo Anthony
Those are the only three that I think Detroit could get and would help improve their team. Actually the odds of Denver trading Melo are slim to none. So Mcgrady is someone I think would actually fit into Detroits system quite well, and if he stays healthy, they could be even more dangerous. It's going to be a tough decision for Dumars, that team is still good, but I think they want their younger guys to get more playing time. Especially Stuckey, Maxiell, and Johnson.