Here what I'm modding and why:
CIV4BuildingInfos.xml
Raised all conquests prob from 25 to 75.
=> I just hate when you lose and then recapture a city and it is back in stone age. With 75% probability, you still have 50% chance of losing each building.
I added a bit of gold income (from 1 to 4 depending of its innate cost) to many building (representing small scale commerce, like selling grains from the granary, etc.). Granary produces +1 gold, Herbalist +2 gold, Public Bath +3, Inn +3, Forge +4 etc.
=> This help play with a bit more gold, I always found that the game was too hard for leaders without special traits like financial etc. It can be related to my style of maps. I play huge maps and I have big drains on gold as soon as I start to expand. Also I like the added incentive. Even if you don't really need an herbalist for the health, you know you get +2 gold and it can help.
Courthouse and Dungeon reduce slightly the global war weariness. Again, in big long games you end up at war constantly. I often had in vanilla FFH size 20 city with WW of 20-30. I really hate that. For me, a huge empire geared to war (or knowing Armaggedon is coming) must be able to sustain perpetual war.
Courthouse gives +1 culture. Culture is influence in fact. A courthouse strengthen the government, so strengthen influence. Same can be said for others buildings.
Aqueduct cost is down to 120 prod and it gives 3 health. I always felt it was too weak. It can now be built (like carnival and walls) by supplies.
Supplies can be built with engineering (cost 120 prod). You can't build forge with it (that would be an exploit). This way, big cities can help young ones. In the end, I perhaps build 6 or so supplies per game, so there is no blatant exploit here.
Herbalist can build Healing Salve for 80 prod.
=> Again, I hate to have a withered rangers for 80 turns in a row, waiting to be healed indefinitely (by a priest yes, but I played Grigori last time and waiting for the Medic was extremely frustrating). If you try, you will see in the end that you don't build much of them, perhaps 3-4 per game.
Research Lab boosted a bit to +20% research and can build the blue and red Salve.
CIV4CivicInfos.xml
Two big changes. First I removed any changes altering food production. Because the AI can't handle the empire-wide effect of having food production altered. It can really screw it completely. So ...
Aristocracy don't gives -1 food. In exchange, upkeep goes to Medium and it adds -2 health.
Agrarianism don't gives +1 food. In exchange, it gives +1 gold per farm and +2 health. Everybody gets +1 food from farm (so a farm gives +2 food not +1 from the start). This also helps the AI in tundra... This way, an AI empire in tundra can still prosper. In vanilla: AI in tundra = very minor empire.
Also...
Undercouncil gives -25% maintenance from distance and -25% distance from #of cities.
Overcouncil gives -50%/-50%
Again, this is because I play huge games. I need to be able to capture enemy cities without having my economy butchered. As these reductions only trigger in the mid game, the early game is still difficult and you can easily over expand. Overcouncil gets a bigger boost, because Undercouncil votes are much more juicy, so it compensates. Now you have a difficult choice between the two.
Experience:
I gave +1 xp to units in both Nationhood and Military state. This allow an empire running 3 military civics to reach 5 xp.
CIV4ImprovementInfos.xml
I cut a bit in the dev time of fort/castles and cottages/town/cities. I felt it was too long.
CIV4PromotionInfos.xml
Bounty Hunter gives +5 gold and only requires Combat II. From my experience, it is now worth to expand a promotion to get it, before I would never do that for 2 gold ... As your empire progress you'll see you don't need the extra gold so much and you'll promote less and less units with BH. Early it can be a good source of income, something like 25 to 50% of it each turn, if you manage well. Nothing overpowering but now it has an interest.
I also reduced by two thirds (yes!) all max damages and damages of all spells, including destroy undead. I always found very abusive the damages levels that could be reached in vanilla FFH. Get one sorcerer with Air 2 and voila, you can completely screw an AI stack. Now you need 3... I know this is a rather big change, but really, it bothers me to no end to see a huge AI stack of 50 units halted and butchered just because you have a single sorcerer. If you are not convinced, do the maths. a unit with 40% damage has something like 1/4 of the chances of a unit with full health to win a battle...
Every spell that create a 'can not move effect' now generates a slow spell effect. It helps prevents the AI remaining stuck indefinitely (I think you know that as soon as one unit among an IA stack has the 'can not move effect', no units will ever move out of the stack?)
Combat I-V now only gives +1 to +3 spell damage.