I have some comments and feedback frist of all you need to get some defensive units for all eras preferably 2 to 3 defensive units that upgrade to each other, for the ancient/middle age nothing is really required (there is plenty of defensive you should have the spearman upgrade to something in the late middle/early industrial age then to Heavy Machinegunner though) but in the late middle/early industrial age you need alot more defensive units and in the industrial age you need more defensive you could just make the Heavy Machinegunner have 20 defensive then have it upgrade to a advanced Heavy Machinegunner that has 30 defensive and so on though the ages. (Making it's defensive match the main Infantrys attack in that era.)
I have two bug reports for the Americans. The Americans can build the Hussar witch in the civilopedia says is the Swedish UU, and American can also biuld Imperial Musketman witch the civilopedia says is the German UU.(I do not no if these are mistakes or on purpose

) and the Cavalry civilopedia entry is invalid.(I still think the Cavalry should upgrade to MechInfantry

)
A couple more things I wanted to comment about, frist is the ships I thing you need to increase the amount of pleople on the industrial/modern age Transport ships, here are some suggestions make the Troop Ship carry 8 units foot units only, the Transport ship carry 12 units foot units only, and the Assault Ship carry 14 units foot units only. Then make three deferent ships that can carry all units but can only carry like 6 then the next ship carry 8 then the next carry 10, this is just an idea that I thought would be cool. I think you should increase the range of navel planes, navel bombers and land bombers.
Now for increasing the cost of techs and boats, I think the Battleship class and aircraft carrier class ships should cost 25% more then what they are now and the techs should be increased by about 25 to 35%. btw I still think the cost of the ships and techs should be increased eventhough I am playing accelerated production
Now to tell you about the game I am playing on a 362 by 362 world map 10 players (I think) the turns are like a 30 to 40 seconds long about 870 AD accelerated production (I love the industrial/modern age) 4 civs died I have settled 3/4 of the united states (I am the Americans) all of Europe is settled 1/2 of Aisa is settled and it is really fun to play(if anybody wants the modified world map I can upload it

, I have to fix some stuff Because the map is alittle missed up)
I have some more things to add, frist you need to put something in-between the brave and minuteman when it comes to upgrading units. You need to add more city improvements and I have some ideas about this. In my mod I am making for myself, instead of having city improvements like water mill, wind mill, and Sky Scraper have it like Industry zone 1, Industry zone 2,
tech Industry zone 1, tech Industry zone 2, etc. but still have the stuff that is all ready in the game and have it where Industry zone 1, 2, 3, 4 and so on cost more then the one before it. (hope you understand I had a little trouble trying to explain it

)