So I built this:
It rode just fine. I used a 14T pulley ( I think 15T would fit as well), the only downside I noticed was that the motor picks up dust way more like this. So ideally, you would have the mount have a thin wall between the motor and the wheel to protect it. Replacing belts is annoying, because you have to remove the whole motor. Also you need narrow pulleys; my TB ones turned out to fit exactly right.