Raul and Marc Kudisch did a duet together last summer, and it fit really well because Marc's voice is so smooth and "classical" compared to Raul's rock(ish) vibrato and all that. The duet was hardly rock or anything like that that Raul's voice can handle, but he still has that quality, and whatnot, so they blended really beautifully together. Michael's voice has that same very smoothe quality to it, so though he sounds completely different and less operatic, I think it would create the same fantastic impact.
A work of art is an invitation to love.