I have written a little Windows application to let other scenario designers do what I have been doing for a couple of months now: namely, turn off buildings in a .sav file.
What use is this, you may ask, when you can already turn off buildings in the scenario editor?
The answer: you can build some buildings of that type, then disallow them after saving the game.
Build one barracks, save the game, then disallow barracks.
Build a walled city, then disallow walls. (See Maracetia in the Africa career).
You want the governor to fight with four cavalry cohorts and nothing more. Build 4 cavalry forts, then save the game and disallow walls.
Build a few prefectures on a desert map, then save the game and disallow prefectures. This would pose a real challenge to the governor, though I doubt that it would be much fun to play.
You want to force the governor to switch over to tax revenue. Turn on flooding and collapsing, build some clay pits and iron mines, save the game and disallow workshops.
It would have been easy to let this program turn buildings back on. To prevent its use as a cheat, I did not. This means that once you use it to turn off some type of building, you cannot undo the change. It's probably a good idea to make backups of saved games before using this program to modify them.