You may need to "Hack it in" by selecting multiple legs, but this would work, and would't be all that bad:

GRR-DTW[or]MSP-NRT-HKG. MSP and DTW to NRT are legacy routes with nice planes.

There is also a route throug LAX that places you in Guangshou (In case you are heading out of the district). The DTW-LAX is quite comfortable on a 767 if you time it right. Again, you may need to manually insert it as a multi leg. Although, be careful as those sometimes create a pricing issue, or a pricing advantage. I've seen both.

Best Of Luck!