It seems to be that would be like a fruit juice wheat, and while it works for juicy juice, I think actually using real fruit with such distinctly different flavors would just end up being a wheat beer with a tart flavor to it.
A blueberry wheat is very tasty, probably one of my favorite fruity beers put out by a local beer company here in Maine called Sea Dog. I've also seen in Boston at a restaurant/bew pub called Boston Beer Works where they take a light wheat and actually put blueberries into the beer when they serve it. Its more a novelty than anything, but its not bad.
To me, I 'd think most stouts have more of a chocolate or coffee flavor to it that wouldn't balance well with a berry flavor.
I'd stick to a single fruit in a light beer such as wheat. I just don't think you would be able to balance it in such a way that you could taste each one.