Changes:
1) Major civs >> Minor Civs and slightly closer to their RL counterparts.
Examples: China - Agri, Sci & Rel. Rome - Ind, Com & Mil. Arabs - Sci, Rel & Exp, England - Seafaring, Mil & Com. Netherlands - Seafaring & Com, Aztecs - Mil & Rel. Iroquoise - Rel.
2) Units & Combat System.
Greater gap in Attack, Defense and hp. Example: Warrior 1-1-1, 2hp reg. Infantry 12-16-1, 8hp reg. Combat not to the death but probability +/- a percentage based on A vs defence with unit strength taken into consideration. Plus a chance of a rugged defence as a joker in the pack.
3) Age of Sail & Naval Units
The years c.1600-1850, ie when the modern world as we know it was formed, are almost completely missing from the game. Caravel & Carrack would come with Engineering, Galleon with Education, Ship-of-the-Line and Frigate with Astronomy and First Rate with Navigation. None of the wooden ships would be upgradable. The English UU would be a Ship-of-the-Line with the stats of a First Rate and the Privateer would be eliminated. Ironclads, non-upgradable, would come with Steam Power and Dreadnoughts with Steel.
4) Corruption Model.
There would be a cap at 60% corruption and you'd be able to build more towns before reaching it. A military presence as well as priestly in the form of Barracks, Temples and Cathedrals would lower corruption. This is in line with RL as religion and the military always have been closely linked with the state. ncidentally, it would give the Rel trait a boost which too is close to RL up to c1900.
5) Pollution
Three levels, each reducing output from tile by 1food-1shield-1commerce. Each level taking 3 base worker turns to clear multiplied by terrain factor, ie lvl 1 pollution on grassland would take three worker turns to clear, a lvl3 pollution on mountain would take 27 worker turns to clear. Pop and Bld pollution would be lvl one and have to strike the same square three times to get at lvl 3 or be left unattended for four turns before automatically reach the next lvl. Nuclear pollution is automatically lvl 3 and will take three times as long to clear. Also, there would be a Sewage Works available with Combustion that would slightly reduce pop & bld pollution.
