Probably not a smart thing to do. Carmichael had more speed and in today's NFL you need to be a deep threat down the sidelines against corner if you're going to be a good WR. Bennett really can't do that. But he can go deep and beat LB's and safeties down the middle of the field against teams playing Cover 2 which leaves the deep middle vulnerable. Or if we put him in a 2 TE set that could leave him one-on-one with a linebacker and throw opposing defenses fits. Plus, Bennett can block which is a nice thing to have. You can go to a 2 TE set and have Bennett stay in for blocking and have Witten still go out for a pass. Protects the QB and still allows an effective receiver in Witten to go out for a pass. Then of course you can do the opposite (Witten block, Bennett go out for a pass) to keep the opposing defense off balance.
Bennett and Carmichael are two very different types of players and there's really no need to move Bennett to WR and if they did and even he was pretty good at making the conversion, it wouldn't solve any problems. I would personally take a guy who can play TE, help out in pass protection and run blocking, beat LB's and safeties on pass patterns and could occasionally line up out wide like a wide receiver than have a pretty decent, large wide receiver. You can do a lot of different and effective things with the former. The latter really doesn't give you much.
YAKUZA