Have a look at Tormenta 2&3 . You'd need a little more reduction again as a longer arm but same principle. I run a gearmotor system too in flatpack but that's pretty useless for you as its 4bar.

Protection wise i'd go one of two ways. Either make it intentionally soft, i.e. thick plastics so it can be broken without massively hindering performance and fixed easily or make it super rock solid, say 8mm hardox arms on a 30mm or so shaft.