Getting a pure FS in the first round would be a poor choice.
Now, getting a good CB in the first round would be a reasonable choice.
Anthony Henry turns 29 this year and Aaron Glenn turns 33 this year. Both of those guys can really play, but are up there in age. They do have Jacques Reeves, who I really like and think he'll be a pretty good RCB some day. However, you still want to have at least 3 quality CB's on your roster and at least 1 serviceable one in case of injury.
Glenn could very well retire soon and while I like Henry as a RCB, there's always a solid chance he could lose too much of a step in the next season or two where he would be unable to be an effective CB because he's getting older.
So, if there's a truly great CB still on the board, I could see why Dallas would want to take him. Especially since this draft is loaded with pass rushing OLB's that they could find in round two.
By getting a good CB, they'd be more than set for the next 4 years with Newman, Reeves, and the rook....along with Henry and Glenn. So, I can see why they would be big on Huff who has quality FS experience. He can start off at CB and they can try Henry (who has played FS in the NFL) or Reeves at FS. If Henry and Reeves are better off at CB, then they could just put Huff at FS for now. Belichick had the same scenario with Eugene Wilson who was supposed to be their CB, but they put him at FS due to injuries and he blossomed.
Other than that, I think they'll almost definitely go after OLB since Wimbley, Carpenter, and Lawson seem like no-brainers. At least one of these guys should be around at #18, if not all three.
Rich...................