How would putting Andre Carter at DE gain you any in the passing game? I doubt Chris Wilson or Jeremy Jarmon are that much better in pass coverage if at all and definitely aren't better pass rushers.
For Andre Carter to even be a viable option at DE he'd have to put on at least 20 pounds to be more stout against the run and he'd would lose all ability to rush the passer from the DE position in the 3-4. So at that point you would have a guy that can't rush the passer from the position he's in and you'd have probably the worst run defending starting lineman in the league. Remember the Redskins are in the NFC East, a division where you play the Cowboys, Eagles, and Giants twice. All teams that run a man blocking scheme with big offensive lineman. Imagine what would happen when you have a 250 pound 3-4 DE thats suppose to be 2 gapping and a lineman that outweights him by 75 lbs or more is blocking him.
I don't see what part of that is beneficial. Be near last in run defense so you can be pretty much the same against the pass.