The descriptions of the difficulty levels say that, on harder difficulty, you get an enemy AI which is harder, as well as one that gets various buffs in things like combat.
I would very, very much like to see these two things separated. I hate playing against a computer opponent when I know it's "cheating". That is to say, when I know that his soldiers actually do 137% more damage than mine, and he makes twice the money i do from the same source, or whatever it is.
Whenever I know that sort of thing is going on, I select whatever difficulty gives no buffs to either the AI or the player, as I want to see how the game is with the playing field level. But in this case, not only am I levelling the playing field in terms of stats, I'm picking the third dumbest AI.
I don't want that. I want to play against the best AI the game can throw at me, on that level field. Give me the option to set the AI difficulty, separate from the game difficulty. That even opens up more interesting options. I could set one enemy to Normal AI, but give him lots of buffs, and another to Smart/No Buffs, maybe a third AI in the middle. That would make for an interesting game!