I e-mailed an EV buddy, and he mentioned that it might be possible to epoxy the chunk o' magnet back in place - so it might be possible. Going to be a big pain in the butt no matter what though!
Here are some photos of what I did this morning (BEFORE breaking the motor...)
Blade motor, ready to sand down.
Blade motor, mostly sanded.
Blade motor, getting a coat of primer, recycled yogurt container keeping paint off the permanent magnets.
New drive-end bearing.
Motor armature with new drive-end and commutator-end bearings
Mower deck up on 5-gallon buckets for testing. One blade motor repainted. It wasn't totally dry when I handled it, so some of the blue paper shop towels got stuck to it!
This is those funky bearings that the steering uses. The grey steel part was completely rusted away on the original bearings. These new ones look much nicer.
I am still very GRRR about the drive motor magnet breaking.... GRRR...