Saxson Violence you might consider a build that would use a foot treadle and a flywheel in your build this way both your hands are freed up and you will not tire out nearly as fast.
Several years ago I started to design a small bench top lathe but never finished the design completely it would probably have been larger than what you are thinking about I had planned on making it a 4inch swing over the carriage with 18" between the centers.
I was planning on using a 3/4" 10 tpi for a lead screw and drive it from a series of bicycle sprockets and chains 3 or 18 sp sprockets sets of different sizes could have given me enough gear changes to do many of the more common threads as well.
I wanted to have a 15 to 25 lb flywheel to help smooth out the spinning rate a coaster setup from a bicycle would have been incorporated to the treadle so I could rock it back and forth or briefly allow my feet to rest.
Now that yo have brought this up I might think about building one myself if I ever run out of anything to do.