I am currently playing Romance of the 3 Kingdoms 6 and one of the important game play effect in this game is the fact you need officers to do all the work in the game. If you do not have enough officers, you will not be able to expand, because if you expand too large you will be too weak and people will bite you easily. So players expands slowly but surely, which is the opposite in civ like games where players expand exponentially.
My suggestion, is that it could be possible to limit exponential rapid growth by requiring officers to expand. But having a complex officer system like in R3K6 would be too much complex for elements. So I suggest that there could be more heroes and that each city requires a hero to be managed. Each mobile army would also require a hero to invade the enemy. A city without hero would mean that the player gather no income from that city. A player would only be able to attack other units if there is a hero in the stack.
It might also be possible to assign heroes to some imperial functions. In other words, make them minister of something to give bonus to your empire.
By using a system like this, it will make sure players will not populate like rabbits, especially computer players. Players will also have a choice between managing larger empires or managing larger armies.
Heroes would be acquired by exploring, searching cities, recruiting from other players, and making babies.