Data is maybe the only one who really could be excellent in any position. I even see him as being a great counselor (certainly better than Troi). His perspectives always shed more light on the behaviors of those around him than anyone else's. It's fairly obvious that he'd be great at everything else.
So the answer is a ship full of Datas? All solved.
Wesley wouldn't be good for captain, security or counsellor, but he'd be fine taking on Geordi's role.
Troi might take up Guinan's role serving drinks and listening, while Guinan might make a good counsellor. There, found a use for Troi.