> Another possible source of data is the driving current of the motors/actuators which is proportional to the mechanical resistance the limb encounters.
The problem is precisely the actuators. A lot of a human's muscles actually come in pairs - agonist and antagonist muscles [1], and it's hard to match the way human muscles work and their relatively tiny size in a non-biological actuator.
Just take your elbow and angle it to 90 degrees, then rapidly close it so your upper and lower arm are (almost) in parallel. An absolutely easy, trivial task to do for your pair of muscles controlling the tendons. But now, try to replicate even this small feat in a motor based actuator. You either use some worm gear to prevent the limb from going in the wrong direction but lose speed, or you use some sort of stepper motor that's very hard to control and takes up a lot of space.
[1] https://en.wikipedia.org/wiki/Anatomical_terms_of_muscle
> Just take your elbow and angle it to 90 degrees, then rapidly close it so your upper and lower arm are (almost) in parallel.
That's trivial with the modern flat motors and position feedback. In fact, motors can do it faster and with more precision than we.
The only reason it was ever hard was because motors didn't have a lot of torque/volume.
The reason our muscles come in pairs is because they can only really apply force in one direction. Motors don't have this limitation, and don't need to be paired.
Anyway, motors still don't have enough torque density for making fine manipulators, and the lack of sensorial data will still stop you from interacting well with the outside world.