I think you are thinking of Banished... :)
Oh, sorry, I thought this was a comment on another game. Duh.

You want a mod that automates the whole game for you? :D

AI behavior can't be touched with the modkit, so that job swapping thing cannot be done I'm afraid.

On the bright side: any worker that cannot do the thing he's assigned to will always revert to laborer mode, so as soon as your farmers have finished harvesting, they'll go and do random odd jobs (clearing, moving stuff, bringing building materials) around the town automatically. They'll go back to the fields again as soon as the season turns to "Early Spring" again (unless it's still freezing, then they'll wait for temperatures to be above 0).
While it's not a perfect solution, it means you don't really need too much micro-managing, except maybe at the very start of the game when you have very few workers.