With all due respect, if you can see that your stout is cloudy, it isn't dark enough!
I'm wanting to say I heard most hefe yeasts produce their signature flavors when combined with wheat grain (which has compounds barley doesn't). Now I've been known to be dead wrong before, so I wouldn't take this as true, but rather something to look into first.
That said, what kind of "fruit" flavors are you looking to get? Anything your typical English yeast isn't going to give you? It may work, but I have a hard time imagining a cross between a hefeweizen and a stout, and an even harder time imagining it would taste good. Still, experimentation is one of the many benefits of homebrewing, so don't let me dissuade you if you like the idea. Consider Belgian ale yeasts as well, as mentioned above (lots of folks seem to like 1762 for stouts).