Interesting but sadly uneffective.

Marking places as "danger zones" ...
Adds only few minutes (at top ... i mean you can get from Waukeen's Rest to te Beach in "few minutes" :-/ so more like few dozen seconds) of walking for everyone who will either want, or need rest ... i know it might seem like "acceptable cost" for those of you who would like to restrict resting ... but for everyone else it is just anoying nonsence that dont really restrict anything. :-/
Repopulating areas ...
That would indeed solve the problem with abusing resting ...
Sadly for the cost of potentialy abusing looting, exping, and wich is worst in my opinion, potentialy making the game unplayable for some people ...
Imagine situation, lets say you go kill Minthara, Ragzlin and Gut ... but you are attacked in camp on sight (for example bcs you knocked out the Twins) ... so whole Goblin base is fighting you, for you as a player its a tough battle (this is still one of conditions, so dont involve your personal skill or experiences ... right now you are player who have problems here) so in order to get through that battle, you spend all your resources (now you see why that condition was there) ...
Now, you can either go fight whole interier of Goblin Base without single spellslot ... or you rest ...
So you rest ... and the camp is full again ...
And you once again get to the point where you have to spend all your resources in order to just survive ...
See how easily you can end in infinite loop?
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Im affraid the only way to please people who demand Long Rest restrictions would be to tie them to the story itself ...
Wich is sadly nerely impossible in game as this one.

But i could imagine it as some popup message saying: "You just arived to Druids Grove, would you like to rest?" ...
And until we make some major quest progress in that particular place ... aka save Halsin, or either redeem or kill Kagha (read it as: Move futher in the story of that particular place, to mimic some sense of time) the message will not show again.
Resting spots would be clearly determined and marked on map ... each would work for single uses (unless renewed by story progression)
And there would be NO other way to get Long Rest, than this.
Short rests would obviously become unlimited and they could even be free.
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Personaly i believe the best compromise here would be either setting amount fo resources needed for Long Rests ...
Or even better, make using food for Long Rest optional, so players who would not like it would need to just work with camp supplies ... and strictly reduce their existence ...
If you so happen to get into tight spot ... you allways have option to simply switch food back on for that one night, and then turn it off again.
It would also give us option for an Achievment ... i would call it Hungry Adventurer
