I have four 15-91s, a 15-125, 201, several 15-90s and a 15-75.
Don't need four but they are hard to pass up.
Mainly use them for all my heavy work. Boots, leather, canvas, etc.
They are tanks. Can't break anything but a needle.
I wouldn't rewire one. Too easy to just find another motor on ebay, etc.
The motor is easy to change out.