A really nice post, you've put alot of thought into it. Most points are well backed by logic. I do, however, have questions about some:
You designated green for well balanced. (Blue Stripes Scout) is not. Crewman is a powerful ability, that pushes this card far above its collegues power curve. Yes, it a reason why NR is played in weather-heavy meta. But its also a powercreep, a card wich has "clear weather effect" for free. Its a patch slapped onto NR to make it viable, but its not a solution. If anything, it causes more troubles.
Dont get me wrong, i see your point. I just dont believe "Clear weather" cards shall be "good" by themselves.
If i were to look for solution, making autoinclude anti-weather card wouldnt be one, auto-includes are a bad thing. Id probably make weather unable to damage armored units, or their armor. Then it would actually require support from cards like WH warrior or archers to get going on core units. Obviously, such tweak would require a revision of armor values, but i digress.
Other points are fair. Id also want to comment on Caranthir - i dont believe him to be broken as is. By himself, hes an interesting card, he does alot, but offer a low power value.
From where i stand, we need more cards capable to endure weather without fuzz (best such card in game ATM is the redanian knight), not autoinclude "iam allready in your deck, and i clear weather for free" cards.