Turn off autosaves in Options -> Gameplay, and set quicksaves to 1 in the same menu. Then play tactician and only use quicksave. This will mean you will always only have one saved state of the game.

This is about as good of a compromise as you'll be able to achieve since having to live with your decisions is contradictory with reloading the save and trying again. You're still heavily compromising the idea of having to live with your decisions because you can just reload the save, but the same would hold true to any mod that works the way you suggest.