This sounds like a great idea! I like the look of this Soviet tractor, basically a cargo truck with tracks. Should be relatively easy to replicate since the basic shapes are flat panels with only a slight curve to the top of the engine hood.

The tank chassis I would use, though, is that of the upcoming HL Panzer III since its roadwheel layout and lower hull shape more closely matches the photos of the tractor you have pictured.

-Harq