I really like this idea personally, and I think with some reasonable limits placed on it that it could be a well-received balance to the current "difficulty" (it's not that difficult) of finding wind shelters.
But I think this would better serve the game not as a balancing factor--which could simply be implemented as a tweak to probabilities in a patch--but as a feature to add some variety to our overall world map strategy.
Some form of time limit could be applied to affected time shards such that the effect would wear off quickly (POSSIBLY even in the middle of an expedition if you lingered too long!). Perhaps you could only be allowed to overextend a wind shelter's shell of protection to 1 or 2 tiles in the allowable regions you outlined, such that each wind shelter would only cover an addition tile or two. By which I do mean a tile or two, not an additional radius of 1 or 2, to clarify.
This might be just enough to give you that extra reach to save spending an additional wind shelter just to get to something that was SLIGHTLY out of reach.
However it were implemented, I like this idea.
Giving us more tactical choices to handle a given problem on the world map adds some needed variety to the overall world-map-strategy side of things. And I do think this would be a more interesting way of handling the current "bottleneck"--which, again, is really not that bad, but could still stand to be addressed.
On a sort of related note--at the risk of hijacking this thread :X--I'd like to see stormy areas possibly become a bit more hazardous/interesting again, but with an added reason to visit them to make them more interesting. :Db I sort of miss the old "beefed up enemy tier" approach, and currently wind shelter missions are a bit boring for all their (ever so slightly) increased danger/PITA factor. ^_^