You'd have to get a NT from elsewhere (draft or FA) to play the 3-4, but I don't think Suh would be completely out of place as a 3-4 DT, and I think you'd get more production out of Jordan Phillips as a 3-4 DT. He may in fact be a natural for it, and his ceiling may be very high.
It may be worth it to make the switch, considering that Suh's talent could probably make up for whatever physical incompatibilities he'd have with the 3-4 DT position, and you'd be elevating the play perhaps of Phillips, Vernon, McCain, and Jordan (if he's alive).
You might also be elevating (or at least maintaining) the play of Jenkins and Misi as 3-4 ILBs, while removing as much of the need for the sideline-to-sideline 4-3 MLB the team currently doesn't have. The run defense suffers in large part because of the absence of that player in my opinion, and a switch to a 3-4 would address that to some extent.
3-4 DTs do one thing. Eat up 2-3 blockers.
For as good as Suh is, he would consistently get moved at the point of attack. And putting him as a 3-4 DT would be a waste of his talents as a penetrator/disruptor.