Those are the two grains I probably use the most, the MO and the Pilsner malt. As base malts go they are night and day in difference. The MO is nice and bready, and I've found has a little bit of sweet like character I haven't found in most domestic base malts. The pilsner is a much clean and drier tasting kind of malt with none of those bready characters.
Using MO in a wit you'd likely lose a lot of those light wit flavors and have something with a more bready English mild kind of flavor profile to it IMHO.