I thought I heard of something similar to this before, but it escapes me. I think this will turn out great, the fruity esters will balance well with the dark roasty malt flavors from the dme. I would leave out the candi sugar, and either increase the dme or simply leave it as is. Just because the color will be dark doesn't mean it needs to be a big beer
Let us know, this sounds very interesting. I've been concentrating on witbiers myself for the summer, and they are my favorite right now. I'd like to see other applications for the wit yeast, which is very unique and basically is the entire flavor profile for any beer its used in.