You could fit a brushless motor in there if it is the same size. The issue is that brushless motors need a controller to work. Otherwise most ( pancake ) motors of the same size run at low speed with very little torque. The faulhaber that is in there is the best you can get in that size.

If you can find a brushless the same size and fine a mini controller that you can cram in there it would be a monster. However if that was easy to do, the stylus would come with one.