There ARE some legit questions about Carter. Is he big enough to withstand the demands of the game. His lack of experience at the position, and his age (which can also be thought of as plus). But in my opinion he would be the IDEAL pick.
FIrst he plays a position of extreme need. We had a HORRIBLE edge rush last year, and though Landry is an improvement, he isn't the solution.
Second he plays a position where rookies can make an instant impact. Like RB and LB great physicality can show immediately and it takes less time for a player to reach his true potential unlike, say, QB, WR or the DL. Of course, he edge players improve over time too, but Carter would be a player where we would see an instant impact on what could end up being a pretty damned good defense.
I'd be fine with Graham, but with the additions on the DL plus a likely return of Baremore he would be strictly a best player available pick. I'd also be fine with Hunter, who is more likely to be there. He'd make the secondary positively scary with Gonsalez. Davis, and himself out there. The schemes he would allow the DC to create would be awesome. And forget about the offensive possibilities even if they are limited. Or the reverse and he becomes a fulltime WR doing limited work as a DB in certain schemes. He simply is the most dynamic player in the draft. The art and skill will be how to use him most effectively to have a long productive career.