I've thoroughly enjoyed Mortal Empires since its release, as well as many other players, so I would like to thank CA for this content.
However, there is a long-living "feature" for Mortal Empires, which is well recognised by players and devs at CA. Certain AI factions tend to steadily dominate the map or be defeated very quickly, like Dwarfs with their "dawitide" or Vlad von Carstein aka Sean Bean. Sometimes the AI meta changes with updates and new DLCs/FLCs (at the moment, Order factions heavily dominate the map).
Anyway, the whole situation feels like it is more driven by updates and non-perfect in-code balance of AI factions, than by player's actions. Some people are upset of fighting the same enemies every campaign.
In addition, different players have different preferences: someone may like to fight the "dawitide", while somebody other absolutely hates it.
Nevertheless, I feel like this problem can be solved easily at least on the level of idea.
The solution is as follows: a player should be able to tune bonuses for big chunks of AI factions before starting a campaign. For example, we can set it at the starting screen like
(a) strong Chaos + strong Destruction + weak Order + weak Undead
(b) strong Chaos + normal Destruction + weak Order + normal Undead
(c) weak Chaos + strong Destruction + weak Order + strong Undead
(d) ... (so on)
By weak/normal/strong I mean (de)buffs to public order, income, recruitment slots, autoresolve, exp gained by units and characters per turn and all that stuff. These (de)buffs are applied on top of those already existing (de)buffs appropriate to the chosen difficulty.
In my opinion, such a "mutator" for AI bonuses will greatly improve sandbox experience side of Mortal Empires.