That would be county workers, not city. The difference in a region like Manitowoc County is significant.
The comment was a response to the idea of the alternatives of killing him or framing him. I was pointing out one reason that simply killing him might not have been the best solution from the point of view of the pols who felt threatened by him.
As far as your response is concerned, I don't think that the idea of framing someone whose reputation had already been as damaged as Avery's was would be all that unimaginable to a backwater sheriff's dept. in a backwater county. After all, they'd railroaded him once before, so it wasn't exactly an unfamiliar concept to them.
County sheriffs in small, sparsely populated places like Manitowoc County tend to operate their jurisdictions like little fiefdoms anyway, with few external restraints on their behavior, and their idea of what is fair is what they want to think is fair. In their minds I expect they felt like Avery deserved to be in prison, whether or not it was due to a conviction for something he was actually guilty of.
Being responsible for the county facing a lawsuit which was asking for more money than the county's revenues in an average year could only add to any predilection they might have already had.
It worked, too. The settlement they managed to work out after they charged Avery for the second murder was only a tiny fraction of that annual revenue.
So, to answer your question, it probably isn't something they would "normally" contemplate doing, but Avery's case was not a "normal" one, and I can easily envision them trying to make the problem of Steve Avery go away by getting him safely tucked back into prison, with an already shredded reputation completely demolished.