There already are outcomes affected by (a single) rest, are you aware of that?
How many are there? I know of a few, and I might have missed some, too!
If you get close enough to spawn that dying True Soul and his two dimwit acolytes but don't interact with them, a long rest will result in the acolytes moving to the goblin camp and leaving his dead corpse lying there. They'll be hanging out at the courtyard party.
A similar thing can happen with Ethel and the brothers if you don't step in. She'll leave their corpses behind and head to her house.
Also, Dhourn in the underdark with his drow party, whichever ones happen to be unpetrified, that is.
If you take a long rest without talking to Dhourn then they'll be gone when you come back. I'm not sure where they go, I just know they're not there anymore.
