Each conquered country should also gives you some unique buildings or upgrades. For example: Astrila - unlocks Trade Post (building, generate gold) Coowana - unlocks Trade Post upgrades (t1 - Trade Post gold produsing increased by 5% for each conquer country, t2 - by 10%, t3-15%, t4-20%) Ija - unlocks Mages Guild (building, produce mages with a low troops effect, but hight power) etc.
Working on it. Will be a bit different than that though!