I had both Fisher Technik and lego, and combining them in one project required some serious fiddling. I'd rigged my own connector pieces, some lego blocks with the stubs cut off glued to some fisher elements. Even without a 3D printer, if you want it badly enough and you can afford to sacrifice a few pieces there are ways to get what you want.

When I was a kid fisher technik was considered better than lego but far far more expensive. There were analog electronic and logic blocks and it was (far) easier to make functioning machinery with Fisher Technik than it was with lego (back then the lego robotics revolution had definitely not happened yet).