Appreciate you sticking around!
Upgrades I agree were a total waste of time and the fact that you contrast them with Reforms being good, is something I would agree with.
Diplomacy was a total rework from Saxon Kings, but I think its heading the right direction considering coalitions are new. It is going to take a few more games to iron out the meta-gaming but it was a good attempt.
In terms of combat I think the aggregate/flat percentage for battles has outstayed its welcome. The next game will probably have combat based on the unit level rather than at the army level.
Nation Wars was intentionally general, it didn't have a theme and was just vague provinces. The goal of the game was for me to think about mechanics. It was always a learning exercise that I would apply to my next theme, either feudal Japan or a rework of my first world war game Battle for Europe.
Thanks for playing the game!