Saying that, the first scenario for Shepard sounds good. He's a little undersized but a proven shutdown corner. He's had some injuries as well but not as of recently.
I've watched Ellis quite a bit down here and he's pretty good but I'd still rather have Dorsey.
Of course, I don't agree with the Allen scenario. We have a top 3 DE in the league on our team and he's only 25. I wouldn't care what draft picks we got. Once again, none of the players coming out of college have proven themselves.