Sometimes, as you know, you have to play the hand you are dealt. Most American would love 3 months off, any time they could get it to ride.
Since the Southern Tier doesn't appeal to you? Have you ever considered Central and South America? The climate is more favorable than in the northern hemisphere. I know an English couple who likes to tour in S.A., especially in Chile. If you would like, I could put you in touch with them. If you are heading down there, an expedition bike, would give you more options.
Although it could be done, with the right equipment, the TransAmerica in parts would not be safe, due to snow and thus no shoulders. If you did the Southern Tier, here is a suggestion, start from Key West, ride to St. Augustine* then head west. Winds will be stronger, but by the time you get to the Rockies, the weather may be a little warmer. (emphasis on little) Good luck to you. Bob *In St. Augustine go to Osteen's Restaurant. The Shrimp is the best!!!!!!!