Generally that unnecessary labor is meant to keep the inmates busy and help them learn skills for after they get out, and the same limits on exploitation of prisoners that currently exist would likely continue to exist. The whole foundation of the penal system is that serving your time is a preferable alternative to getting shot - if the punishment for a crime is being turned into a meat puppet then every shootout is to the death, no one ever makes a plea deal, and every prisoner riots. We already place some pretty significant limits on how badly prisoners can be treated, there's no reason to think these restrictions would magically disappear.
And this doesn't change the fact that all the expensive parts of automation remain for this case - the moment you stop controlling the human body with a human brain, you need to program every individual bodily movement. You still need to provide food, water, rest, and medical care to these people or their bodies will stop working. Biological variation means you don't get near-mechanical consistency, and odds are the expensive programming work you did isn't even transferrable between different bodies. In fact, normal fluctuations in fatigue and adrenaline and bodily changes like increase in muscle mass mean your program may need modification from one day to the next. By comparison, robots are cheap, strong, and reliable.
Yes, you get the benefit of restricting people's freedom of movement, but you know you can also do that with a straight jacket, or holding a gun to their head. The same goes for sex workers and suicide bombers and anyone else you would seek to control against their will - if you have the means to force a puppetting device on them, you almost certainly already have the means to force them to do anything else you might want.
Maybe if you took the technology far enough that someone could be almost instantaneously puppetted via a non-invasive procedure and the equipment was small enough that no one could tell the person was puppetted you could have some real issues with the ultimate identity theft, but I imagine by that point technologies both to prevent oneself from being puppetted against their will and means of detecting those who are being controlled would be available.
And this doesn't change the fact that all the expensive parts of automation remain for this case - the moment you stop controlling the human body with a human brain, you need to program every individual bodily movement. You still need to provide food, water, rest, and medical care to these people or their bodies will stop working. Biological variation means you don't get near-mechanical consistency, and odds are the expensive programming work you did isn't even transferrable between different bodies. In fact, normal fluctuations in fatigue and adrenaline and bodily changes like increase in muscle mass mean your program may need modification from one day to the next. By comparison, robots are cheap, strong, and reliable.
Yes, you get the benefit of restricting people's freedom of movement, but you know you can also do that with a straight jacket, or holding a gun to their head. The same goes for sex workers and suicide bombers and anyone else you would seek to control against their will - if you have the means to force a puppetting device on them, you almost certainly already have the means to force them to do anything else you might want.
Maybe if you took the technology far enough that someone could be almost instantaneously puppetted via a non-invasive procedure and the equipment was small enough that no one could tell the person was puppetted you could have some real issues with the ultimate identity theft, but I imagine by that point technologies both to prevent oneself from being puppetted against their will and means of detecting those who are being controlled would be available.