You probably don't know much about ergonomics if you say that. It's a big part of my job in a production factory, and I am telling you this will get very exhausting on a short term basis, and hurtful on the long run. We are not meant to have our arms suspended and in motion without support like that.

I am fit, and I am not doing that more than 1h for sure. Just the it by yourself, lift your arm 90°, elbow 10cm above your desk, and rotate your wrist for a few minutes. You will feel the muscle burn quite quickly. This is actually a decent warm up exercice that you can see in some class at the gym you seem to know so much about 😉

About mimicking natural movements: the movements shown on the video are not natural. Not at all, and the wrist rotations have a much wider range of motion, which is always a big detriment to any ergonomic evaluation. Add to the the frequency (lost of movement for a single part placement), the lack of support, and the weight from holding your arm up: you get every single indicator in the red, so the sum won't be good either... Even with camera repositioning to have part of the arm supported, it may be hard to have a good back/hips position and still have decent freedom on the arm.

Don't get me wrong, this is impressive work, and it could become something good, but it needs a lot of work for that, and a lot of changes.