Usually, vertices are not arranged in nice lines and do not form flat slices so it is not that easy to cut models at any place randomly, maybe it would be possible to make some algorithm which can calculate intersection between 2 surfaces, but it will still require considerable human editing

I think you would end with something similar to the lego blocks that can be glued together into something bigger

If you only want to make some random stats this is, of course, no problem at all, but if we want our monstrosity to move and behave somewhat reasonably it will be considerable problem.

I guess it can be somewhat solved by some kind of algorithm where simulator will try to find optimal way to control every arm and leg to maintain balance while moving.