I think most of us agree that the current balance for the civs is pretty good. However there are some civs that need some tweeks. Here are a few suggestions from me:
Burmese: Swap their unique techs, and change its prices accordingly. Howdah its more of an Imperial Age tech, and the new effect of Manipur Cavalry is more useful for Burmese in Castle Age, where they struggle the most.
Byzantines: Greek Fire doesn´t low the accuracy of Fire Ships.
Cumans: Feudal Town Center is constructed 50% slower. The problem for that bonus is that its way too slow to build. This would make their feudal boom more viable.
Indians: Shatagni doesnt low accuracy from Hand Cannons.
Italians: Silk Road: Reduces the cost of trade units by 33% to all team members. I think this would be much more userfull in team games, but to counter balance the effect, the discount should be reduced.
Lithuanians: Relic bonus is capped back at 5. Now that Blast Furnace has been removed, I think it would be fine if the original cap for the bonus is restored. We still wouldn’t have those broken Paladins from DE’s release day.
Mongols: Nomads now affects destroyed Town Centers. Just to make that tech a bit more usefull :v.
Portuguese: Organ Gun: Restore the original +1 bonus against infantry. Organ guns are a completely useless unit, they should get at least an anti-Infantry theme.
Saracens: Madrasah: Change effect that monks cost 33% less. Again, to make another useless tech a bit more usefull.
Spanish: Bloodlines and trash unit upgrades cost no gold. I think this bonus would make a good sinergy with their goldless Blacksmith upgrades. The bloodlines one would be specially great to improve their early game.
Turks: Any idea how to change the gunpowder techs costing 50% less? Back in Age of Kings it was a good bonus, but now that the only techs that applies to are Bombard Tower and Elite Cannon Galleon, its pretty useless in open land maps.
Vietnamese: Conscription no longer free but available in Castle Age. For me Vietnamese are fine, but I think it would be a better bonus.