The Hobbyking Rotomax series of motors might be interesting; I have been rebuilding one for a weapon motor and the construction is pretty good. They are not sensored but the internals are so large that it would be very easy to glue in the sensors yourself. For even larger brushless motors, check out http://kellycontroller.com/index.php. they have ESCs that would work with the Rotomax motors and a range of brushless hub motors (as long as you don't mind large diameter wheels)