If you're looking for comments, I personally don't like the idea of gluing in a motor into the gearbox. The cheap brushed motors don't last that long and if you can't get the motor out of the box, that adds another few bucks to the repair.
The idea is a good one for people looking for a direct drive solution though and don't care about the potential extra cost. I might look into a different means of securing it though. Would it be possible to drill a couple of small holes into the motor and screwing it in through the top of the gearbox? Or what about one of these:
http://www.backyardflying.com/secure...6438186.2.html
Could you friction fit it using plumbers teflon tape or small bits of tape?