Roughly six months ago I saw a story online somewhere about a computer programmer that came up with a route to hit all 48 state capitals in the shortest possible driving distance. Not that it would help you with your planned journey perhaps but it would be interesting at least a starting point.
I think you need a map with all the northern states in blue where you don't want to be in the winter time and all the deep southern states where you don't want to be in the summer time perhaps in red. Then color the spring and fall weather States some other way. But the Pacific coast could have an extended seasons for you so maybe some special consideration there.
Sounds like the heck of a way to spend a year but if it is nose to the grindstone work then perhaps not.
But anyway, have fun.