There is some observed evidence to suggest that if the METAR injection were simply disabled, then the fallback result really could be weather of pre-SU7 quality.
This has been noted in a few cases where the METAR injection service was temporarily unavailable, and the sim had seemingly reverted to a much more authentic looking environment such as existed before “blending” became a thing.
The thread Weather like pre su7 before 8 AM UK time, photos and videos provided!2 contains footage and multiple reports of such cases.
So there is indeed reason to at least suspect that a simple off switch could possibly bring back the glory that was the single-source, unblended, weather experience that the sim is really capable of delivering.
It would be a very simple experiment for Asobo to try, or just put up the toggle so that we can try and see what results we get. If the data is being blended in the sim, then at some point, there must exist an undisturbed set of wx data from MB, which is then combined with other sources (to it’s ultimate detriment, alas).
It isn’t at all clear whether this is done locally in the sim, or if it happens on the server side.
In any case, leaving this data undisturbed as it enter the simulation is really a matter of not doing things to it, unless they really took a very destructive approach to development and removed functionality instead of building on top of what was already there.
Perhaps now that there is a weather debug panel, we can try and dig down to puzzle out just what data comes into the sim and in what forms. Depending on what is and isn’t there, we might be able to learn whether or not a client-side bypass of wx blending is feasible and to what results.