I don't like the idea of 2 Short rests equal night because then you have no Short rests for night adventuring. Just a simple Day to Night button would work fine, implying your party waits until night to adventure. Then you can go as long as you want, short rest twice, etc, just like during the day. Then, when you long rest, boom. Night camp scenes. You wake up and it's day. Hit the Day to Night button if you want and boom, transition to night.
