So there is just one option left as I wrote above. No long rest at unsafe areas. That's it. You wanna long rest after every encounter before clearing out the whole area, then you have to run to the last safe area then teleport to your precious camp. .
It's a good idea but I don't think it works with this game engine. What's an unsafe area? How does the player know it's unsafe?
The camera doesn't zoom out very far, and personally I hate games that say "You cannot rest, or save, or whatever because enemies are near!" when the game isn't actually showing me what enemies it's talking about.
I agree it's an exploit if you see a group of enemies and move out of range to rest, but that isn't always the case. It's hard to avoid that situation where the game doesn't let you rest just because you haven't uncovered the closest enemy group yet. And then it's just busy work for the player to scout around and find out where the darned enemies are that are preventing the action.