My vote would be a Singer 31-15 or 31-21 industrial.
The 31-15 uses the regular class 15 bobbins and can be used for anything from tailoring to blankets, canvas and oiled cloths.
The 31-21 can be used for leather like sewing shoes and light saddles. The max rpm for these machines are 2200 rpm so they really fly but could easily be slowed down to a comfortable pace.
Depending on how heavy the material you could use a Singer 29, I am looking for one of those for my long arm quilting, treadled of course!!! :thumbup:
Billy