I think having an “objective” hex that only provides income would be the single greatest improvement to the tactical aspect of the game.
Currently the fact that an enemy unit can pop up on a base means you can’t have objectives that are not easily defended.
These could be a base that does not produce. But It could also be an Icon that overlays the terrain.
There could be several, that have varied or definable values.
Barn icon : Farm 20 coins
Pick axe : Mine 50 coins
Oil derrick : Oilfield : 100 coins.
These could also have no, less or variable capture delays