Here is the list of my modifications so far and I might have some more in the future.
UNITS MODIFICATIONS
Diplomat - increased movement from 1 tile to 2 tiles and changed its enabling advance to Writing
Machine Gunner - increased its defense from 40 to 45 and changed its enabling advance from Industrial Revolution to Mass Production
Longship - incrased its attack power from to 0 to 10 (could not understand what Activision was thinking) and changed its obsolete advance to Cannon Making
Ship of the Line - increased cargo capacity from 0 to 3 and decreased its attack from 35 to 30
Troop Ship - increased its movement range to 6 tiles
Carrack - changed its obsolete advance to Naval Tactics
Fire Tireme - changed its obsolete advance to Chemistry
Warrior - changed its obsolete advance to Monarchy
Mounted Archer - changed its obsolete advance to Feudalism
Knight - changed its obsolete advance to Cavalry Tactics
Cavalry - changed its obsolete advance to Tank Warfare
Catapult - changed its obsolete advance to Gunpowder
Destroyer - changed its obsolete advance to Ultra-Pressure Machinery
Hoplite - changed its obsolete advance to Fedualism
Samurai - changed its obsolete advance to Gunpowder
Pikeman - changed its obsolete advance to Cavalry Tactics
Submarine - changed its required advance to Internal Combustion
ADVANCES MODIFICATIONS
Facism - changed its prerequesite advances to Industrial Revolution and Mass Media
WONDERS MODIFICATIONS
The Great Wall - changed its military war preparedness cost to 75% reduction
Chichen Itza - entered an obsolete advance to Age of Reason
BUILDINGS MODIFICATIONS
Factory - changed its increase in production to +25%
Robotic Plant - changed its increase in production to +25%
TERRAIN MODIFICATIONS
Forest - changed its shield amount to 15
Beach - changed its food amount to 15
Continental Shelf - changed its food amount to 10
Water Ridge - changed its food amount to 10
Desert - changed its food amount to 5 and shield amount to 10
Jungle - changed its food amount to 10 and shield amount to 15
Mountain - changed its shield amount to 20
These are the only things I have accomplished so far. I want to do some modifications for Infantrymen by changing its name to Musketeer, its technology requirement, and its stats. But first I want to add a Rifleman unit. Has anyone done this yet? Thanks for any help!