[Skyentific] is looking to push the hobbyist robotics state of the art. Motors and their gears, the actuators, are typically the most expensive part. For his build, he realised he needed big servos ...

It’s little secret that stepper motors are everywhere in FDM 3D printers, but there’s no real reason why you cannot take another type of DC motor like a brushless DC (BLDC) motor and use that instead.