I have entertained the idea for some time and finally found an ice cream freezer motor...high torque, low speed.
A friend of mine and I plan to develope the idea as soon as time permits using a "straight sided" keg. All stainless paddles and shaft.
If you have a 10" opening in the keg, this motor will fit perfectly.
With a well insulated mast tun and heat control... oh well you get the idea...more gadgets and fun!!! ;D