Here is a summary of the ideas so far in the thread and some comments...
Champion Stack of Doom
Split XP (Stupidity10)
Sounds like this is on the way. Should be part of the game anyway.
Champion conflicts (AlLanMandragoran)
Interesting concept. Would increase RP but possibly add stack micromanagement - but this is the the most interesting aspect of the game.
Positive incentives to have fewer champions in stack rather than forced to do it (CdrRogdan)
Yes. I think this is important. Need to always give the player choice rather than forcing a way of playing.
Non-stackable troop bonuses (CdrRogdan)
This is critical I think. Should be part of the game anyway.
Troops to hire around map more than champions (OrleanKnight)
Love this idea as it would promote an 'army' rather than a 'fellowship'.
Start with all War techs (OrleanKnight)
This is a great and very important idea!!! Why limit what troops you build based on war tech? There is already a limit is on resources and affordability. This would allow you to CHOOSE the size and power of troops from the start and you would need to balance that with what you can afford. Weaker garrison troops and strong front-line troops etc. Hope this is seriously looked at! Love it.
Champions tied to quests - and fewer of them (OrleanKnight)
This is a good idea to limit the number and make them more special.
Recruit champions from troops (OrleanKnight)
Don't really get this idea. Sounds a bit complicated.
Easy upgrade of equipment (OrleanKnight)
Yes. Important idea. Select troops should be able to be kept geared up as long as you have the resources to do so.
Easy recruitment of conquered monsters (OrleanKnight)
Like this idea too. Your army would be a collection of defeated monsters, your built troops, and a couple of champions. Interesting every time you played!
One leader per stack (lokiju)
I'm in favour second to positive incentives - but I think we would be in the minority.
Cap unit numbers (Dreadcough)
If you didn't get such a massive bonus from capturing cities then the limit would be on the wages you need to pay. Agree with concept though.
Champion upkeep (EvilMaxWar)
Yes. Would create a degree of parity between champions and troops.
4 Champions per group (LordRikerQ)
Like the reasoning but feel the positive incentive the is the better way to go.
Cooldown for champions completing a quest (Civfreak)
Would add to the micromanagement I think. And as you pointed out, there would most likely be exploits.
Adjust experience curve to make levelup harder later in game (Sythion)
Splitting XP will help with this anyway I think.
Champions charge for service based on level (Guryon)
(Hi Guryon - it's me, Splat from TOG ) Similar to EvilMaxWar's suggestion of champion upkeep.
Champions cannot overpower an army on their own (Michael_Zett)
Champions would become generals. I don't mind that but I think others would disagree.
City Spam Hell
Resident champion in city. Outposts to cities if housed by a governor (ajax bomb)
Could add to the micromanagement but would help to keep down the number of cities.
Limit to growth after a certain number of cities (CdrRogdan)
I actually thought they were going to try and do this anyway. But you still have a problem of what to do with conquered cities.
Forward bases (OrleanKnight)
Don't really get this idea. Sounds complicated.
Unrest on conquered cities (DsRaider)
Would add a bit to the micromanagement. Would prefer a simpler solution.
Slow time to raze cities (DsRaider)
This should be part of the game.
City build checklist and improved city UI (Sythion)
Should be part of the game no matter what decision is made.
Homeland cities and vassal cities (Das123)
What a great idea!
By mid-game new cities start with basic buildings (Michael_Zett)
This doesn't solve the balance issues for me. I want fewer cities on the map in total, not more cities.
AI Governors (Michael_Zett)
Should be part of the game anyway.
AI banding together against player to match discrepency in score (Wizard1200)
Should be part of the game anyway.
Archer towers (OrleanKnight)
Nice idea. Would make attacking cities much more interesting.