Hi Russ,
Jesse has done a great job with Motor! As far as I know no one has tried to integrate MongoEngine and Motor.
I can think of a couple of starting points:
1) pseudo code what using mongoengine with motor would look like - that might give you some starting points
2) look at how mongoengine uses pymongo and see how that could be replaced with Motor syntax.
I dont think it would be a small job, but start small and hopefully it will help improve the mongoengine code base for sync or async users alike!
Ross