I can remove and replace a villager's workstation as often as I'd like while the game is continuously loaded, and they behave as expected (lose profession immediately, regain profession with new trades soon after replacement). However, after saving and exiting, and then logging back on, in order to remove the villager's profession, I have to destroy the workstation, and THEN place down another workstation corresponding to a different profession. At that moment, the villager will change from his previous profession directly to the new profession, without going through the intermediate unemployed state