A list of boni I made a while ago:
Eco boni from various mods which I really like:
Economic techs available one age earlier
- Towncenters spawn 1 Villager in Feudal/Castle Age; Towncenter build in Castle/Imperial Age spawn 2 Villager
- Farms are 2x2 instead of 3x3
- Mills, Lumber Camps, Mining Camps are mobile but have slightly less HP
- Blacksmith upgrades are automatically researched for free an age after they become available
- Upon Age, receive 1/2/2 free villagers.TC built in Castle Age spawn 2 free villagers
- Villager work 6% faster
- Drop-off buildings merged
- Eagle Warrior upgrades free
- Castle Age upgrade 25% cheaper
- Economic units return 50% of their cost when killed
- Start with +2 villagers but -150 food
- All units cost 5% less
- Receive 50 stone and 100 wood per age
- 5/60 wood 4/50 food and 0/15 stone per minute generate in Dark/Imperial Age
- +5 Villager HP for each Towncenter technology
- Can create Cows from Town center which cost gold. Cost gold
Blacksmith techs cost -50% food - Dropsites research at twice the speed.
- Castles get +2000 HP (probably too strong)
- Towncenters (TC bonus starts in Castle Age), Houses, Docks and Markets build 40% faster
Gold mines last 30% longer (=240 gold more each tile)
Bundle 2:
- Villager +1 range per Age, benefit from Fledging, Bodkin Arrow, Bracer and Chemistry, do pierce damage.
- Villager do +1 damage vs villager (to compensate that they do pierce damage)
Military boni:
Siege technologies 40% cheaper
- Infantry armour technologies affect cavalry and archers, whose armour technologies are no longer available
- Pikeman +1 range from Castle Age on
- Barrack upgrades cost no gold
Stable upgrades 50% cheaper
Chevalier available in Castle Age (Probably without Blood Lines) - Fletching, Bodkin arrow and Bracer are free, but require a blacksmith
- Projectiles are faster
- Stables and scouts can be made in the dark age
- Spearmen available in Dark Age
- Archer-line upgrades free (too strong probably)
- Archer line benefit twice from Bodking Arrow, Bracer and Chemistry (no Crossbow upgrade)
Sources:
The bold ones have been used either as balance measure or are part of new civs now.