Japan (from what I hear), has poor people who are still physically capable stand and guard construction sites. Personally I can’t see anything particularly horrible about this (though I don’t know what the penalty is for not doing it.)
I think that the main issue with a workhouse, though, is that the only way to make it self-sufficient in the real world is that it would have to be a miniature economy. But anyplace that has to take anyone in is going to be dragged down by people who fell out of the real economy due to laziness, alcoholism, etc. Certainly, some X percent (possibly the majority even) will relish the prospect of being able to find employment, but it’s hard to work with and particularly to manage a place where the other Y percent of everyone is just looking for a handout. And once the people in charge start having to separate “the good from the bad” or trying to make the bad work regardless, nothing much good will come. You’ll get cases of beatings, bullying, etc.
Possibly with a setup like follows, you could get something that works:
There’s an open yard/tent with a work-area, and an office in the back with a window. In the morning you go up to the office and sign up, then go to work. Note that there will be no one “managing” the work-area–just guards or something to make sure people don’t destroy the machines/tools or do anything dangerous (i.e. bouncers.)
At the end of the shift you take all the widgets you made up to the office, and for that they let you in for lunch. The more widgets you made, the larger a menu you get a choice from (or you can bank your points.)
Repeat for the afternoon shift, and getting dinner.
Showers would be open to all (maybe one job would be to clean people so that the amount of water used per person was kept constant.) Lodging would require that you had made at least W number of widgets that day (W adjusted to match how much housing room they had.)
I.e. you try to set it up such that there really aren’t any sort of manager people. People can come and work or not, up to them. But the more work they do, the more benefits there would be.