I like #3 the best, but may be very difficult to implement correctly while telling the story that Larian is attempting to tell.
Discussing this with friends, we have gone back and forth and around and around. Where I’ve finally landed on is...maybe just keep it simple. Gate certain areas where it’s safe to rest, areas where there is a probability of getting ambushed and have a significant disadvantage during the battle, and other areas where you just can’t camp. You’d have to make a clear path out of the dungeon before you could “return to camp”.
BG1 & 2 were similar to this and those games were “ok” 🤣
Makes sense, at least if Fast Travel is also off in the "blocked" or dangerous parts.