"I basically need a sort of one shot machine that can do most things."
Ahh, the mythical unicorn of sewing machines. Every leatherworker who uses a machine would like one of those. Paradoxically, the machine that comes closest is also one of the biggest/heaviest, a 441 clone. Using a modified needleplate/feed dog, as made by a couple of members on here, it can sew using very heavy #347 thread down to #69 (if you can find the right size needle). BUT they are big heavy machines!