To be fair the main qualm here is plains. Mountains offer - mostly unneeded but kinda working - beast buildings and lairs, but once you get plains, the things with the biggest cities in the game, you got huge blanks. And the watery plains you lack lv III to build the aqueduct for IV which then would also lack another building for the new slot.
And no building raid camps is the most useless building I can imagine. Even the ♥♥♥♥♥♥♥ of RP buildings is useless past turn 200 for nearly all factions. It would be different if you allowed excess RP to reduce cooldown time of spells. Then it would be important to the last day!

So Icespire needs: 1 more building to build instead of raid camps for plains in general. A lv III building for plains to activate aqueducts when available and other 2 more possible buildings to fill the tab for lv7 provinces without rivers etc.

I accept that Icespire has to scrap the barrel for money as it does not have "government" buildings with direct money to treasury... so don't add those. But maybe some more that reduce upkeep for their troops in plains to build military stations in those huge plains? I can use forests for the archer doomstacks of mass moneywaste and hills to build one of the 2, that is fine. I never use beasts, but lairs are also fine to be able to.