It's certainly really interesting. I can see this happening. A bit of problem with the flow though, I can't quite imagine Watanuki and Yuuko conversing in English. Yuuko maybe, but not Watanuki and certainly not to each other. If Draco understanding them is because of black Mokona's presence, it would've been a little clearer to make an observation of it.
Other than that a really original read :) So, what did Draco get in return for his payment in the end?