it is far from perfect and even worse for the battle AI. It is now all too easy to take down the AI's arty, and you hardly can defend your arty (or other weak units) properly. It's a nightmare, and i am really stunned that alot of people don't see that.
Exactly, and I've given this quite abit of thought.
CiV could be easily modified to prevent the rout of AI archer and artillery units - units that in real life would always be supported. It would also prevent these support units preventing the AI deploying their forces effectively - archers preventing the deployment of swordsmen etc.
The solution, is to give support units such as archers, crossbows, artillery, anti-tank etc the same stacking ability as Great Generals.
Then these units can be easily protected by spears and such instead of being destroyed easily. These support units would no longer road-block the AI offensive units and the AI would stand a chance - it would also stop us just riding down countless archers and artillery with our cavalry.
Such a simple change, could significantly improve the game. I may even look to make a military mod at some time to fill this 'need'. I'd rather it be in the game as I love STEAM achievements.
Another way this change would improve the game is by bringing back combined arms, even in a limited fashion. Anti-tank guns, being mixed up with infantry makes sense. Not having them operating separately. Anti-aircraft guns deployed with infantry or tanks, makes sense. Having them deployed on their own and entirely vulnerable to ground forces makes no sense. The AI can't protect these units and countless numbers are easily destroyed - it is daft.
One simple change to certain classes of units could make a vast difference.
But, I'd also apply it to naval units. Naval units such as aircraft carriers should stack with AEGIS cruisers/CiV equivalent which would form a close escort. It should be possible to actually have a destroyer in the same tile as a embarked unit to provide close support - in convoy. As it is, it makes no sense and military concepts such as the convoy are not a feature of this game as any significant movement of ships or units takes up half the ocean because each vessel or embarked unit takes a tile.
1UPT has some nice features, but I think it is overkill ultimately and makes the game worse as by preventing combined arms, it allows the AI to be slaughtered as single player moves aren't simultaneous - at least in mp you can counter-attack, or move units immediately in response. Enforced as it is, just doesn't make sense as military history is about the concentration of force at a particular point, god help anyone trying to simulate WW2, you'll need a vast map if D-Day is going to be represented in any meaningful fashion.
If it was me, I'd also change the 1UPT for certain terrain. I wouldn't have it apply to naval units. I would have it relaxed in certain terrain types such as grasslands and plains, I would have it relaxed in tiles containing roads/railroads that would allow more units to deploy and be supplied.
I'd keep 1UPT for forests, hills, jungle, ice and desert etc. Terrain types that limit the deployment of units, but, in grasslands where large armies could deploy easily. It would encourage invasions along open terrain types and limit invasions across more tricky terrain - as in history.
1UPT was brought in as stacking was an issue, but it was overkill and makes for major pathfinding issues, makes the AI even more ineffectual and is even less realistic. It needs tweaking to allow limited stacking/escorting at the very least.