I'd like to see the game differentiate between hero stacks and army stacks.

I'd like to see the default military unit size increased to 5 individuals.

I'd like the introduction of a new Adventure tech enabling factions to create "adventuring companies" - hero stacks.

I'd like the game to require that hero characters & sovereigns join a retinue to join an army stack.

I'd like hero stacks to be unable to attack army stacks and settlements.

I'd like hero stacks to be able to disrupt production buildings (farms, gold mines etc.) for a number of turns.

I'd like to see the currently available info on enemy cities hidden unless a hero with the "thief" ability is within the city's influence zone.

I'd like to see severe and global diplomatic & reputation penalties for attacking a hero stack with an army stack.

I'd like army stacks to be unable to explore notable locations and go on quests.

I'd like the game to provide a proper quest journal, and for the game to enforce that only the hero stack that initiated a quest can accomplish it.

I'd like factions to be able to bribe hero stacks without a sovereign to switch faction allegiance.

Of course, none of this would work all that well without ditching every last bit of the current combat & character development systems, in favour of something not-utterly-broken. But then, the current combat & character development systems are utterly broken, so that has to happen anyway.

I can go into very fine detail about exactly how I'd like my above suggestions to work, and/or offer you guys complete, functional & not designed-to-breakdown.in-suckitude combat & character development mechanics, if you'd like. But vaque suggestions seem to go over better with you guys, and I'm not about to write 30 pages worth of game mechanics if there's no chance you'll even consider them.