It does! I am happy that what you're doing sounds like a possibility. In the few threads I saw some stuff about brushed motors, and thought you were very confused.
For what its worth, I think this might depend in part on how to take apart the motor safely. You should have wires going into the motor if has an internal controller, and if you follow those, presumably you will get to an internal controller. There's a chance it's epoxied in, which will be hard to deal with. But if you're lucky you will simply be able to remove the internal controller. The internal controller will still work the same way, and have three wires go to the motor. Those might need to be extended, but if you extend them out of the motor with new longer wires [use thick gauge for these 'phase wires'] and you'll be in a good position to wire up an external controller. I do not think there should be any problems with this, but I would search endless-sphere for some of the magic pie mods. I think if you can't find the mods for the BMC you speak of, you are likely to find some about Magic Pie, another company that sold internal and external controller motors. Plenty of people had their internal one blow, and had to replace it with an external one.