Originally Posted by BrookdaleBrew
I actually think it could turn out great. Stone did a beer last year that was an Imperial Porter brewed with Belgian yeast and it came out awesome. Those spicy/estery yeasts can do some cool things to dark beers.
One of these days I want to brew a big chocolate stout, but ferment it with hefe yeast at a high temp and make a chocolate banana stout!
I tried the Heffewiezen yeast in a big stout once - a clone of the Yeti - and let's say it wasn't a great idea. It amplified lots of flavors that weren't meant to be amplified and I got a really astringent beer. I pitched it on top of a yeast cake from a fairly strong double Hefe (7.6%) - and the yeast fermented an amazing wheat wine after the Stout. They fermented my wheat wine pretty dry and it tasted great, but the stout was really yucky.
Maybe it's just luck of the draw to which yeasts work and which don't. I'd try it on a small batch first.