It's been suggested before. Thought I'd bring it back up as a fun way to address the persistent issue with the pushover AI factions. Other similar games have this feature.
All the way back to EWOM, this series has only ever given me fleeting instances of feeling the need to build armies, or recruit many champions past my initial few. The AI is simply too vulnerable to military steamrolling by a few powerful champions or units. I wish I could say it was only an early game issue, but the player becomes far more dangerous with increased levels and tech than the AI does.
Hopefully, as we near the home stretch for the development of the game, the Devs will be finally able to sort much of this out with combat re-balancing.
But I think to some extent, the AI will never really be entirely able to cope with the player ability to min max and focus-develop super champions, unless champions get nerfed to the extent that they no longer become fun to level up, in which case I think you lose a good chunk of the game's appeal.
It might be fun, if each faction had their own unique guardian monster in their capital city (only), that leveled up with the city, becoming more powerful, so the longer you let the city grow, the more of a fight you'll be in for to take it down. I'm thinking something that starts about as powerful as a slag or a golem, and ends up just under the power level of the unique monsters in the Wildland regions. Something that required an army, or several highly developed champions to take down, that you could not realistically expect to defeat in the early game. Defensive only, like the City Militia.
Here's what I envision results from this off the top of my head:
1) It helps the AI Factions survive the early game.
You can beat them down, but not entirely out at first. Skirmish over property and resources. Conquer their annoying little cities they build on your borders. But eventually you might actually want to sign a treaty, giving them the chance to rebuild somewhat, and become a threat again. The game needs reasons to open that diplomacy menu. It has precious few at present.
2) It creates an "endgame".
The battle for map conquest becomes more epic, and stretched out with more back and forth over the course of the game. Skirmishes and treaties mark the early game, with more back and forth, meanwhile both you and the AI are still able to build up to an epic final clash to take out their capital later in the game, where you can actually see some of those late game units, knights in full plate, and powerful monster units, instead of most of the AI factions falling at the spear-man level.
3) It adds yet another opportunity for Faction differentiation and flavor, which we can't get enough of.
Each guardian should be unique, and indicative of the Faction's personality. People might actually find the guardian a reason to favor one faction over another.
Like I said, I'm hopeful the devs will solve many of these issues with re-balancing. But I dont think it precludes something like this either. Just an idea, and not an original one.