Some very good posts Boris, I agree with a lot of your ideas. Would you be interested in trying to work on a mod once we settle into BNW?
Some comments on your posts. Firstly, the one dealing with infantry:
I generally agree with everything you say. The only thing is that I think a "magazine rifleman" might be superfluous. Not historically, but in terms of gameplay. I really hate the clutter of too many units, and some that are obsolete as soon as you build them. It might be worth making the rifleman a slightly later unit and infantry a slightly earlier one. In terms of other units in the game, Artillery and Landship would arrive (roughly) 2/3 of the way between rifleman and infantry, tank a little after infantry, and modern armour and rocket artillery a little after mech infantry.
Game play wise, this gives a couple of windows in the late game where offensive power is stronger than defensive, and many others when defence is stronger. Makes for more interesting wars and power plays than if everything levels up at the same time.
On the cavalry ones, I think you have far too many cavalry units. Choice is good in a game, but clutter is off putting and helps no one. If a unit is such that you might build it 1/5 games (where you reach that era), it's probably not needed. The way I did it in my mod "9 Ages of War" is to have each era have either a light cavalry or heavy cavalry unit (with independent upgrade paths), to reduce the number of units; give each a window when they're very good, and a window where they are just acceptable, to encourage more careful timing and planning of wars depending on which unit type you have decided to focus on.
Light cavalry (generally 5 or 6 movements, weak strength, but +33% or +50% against ranged and siege units):
Ancient: chariot archer (no longer ranged. 3 moves, double on flat terrain)
Medieval/Classical: Skirmish cavalry (unlocks at machinery, armed with small spears/bows)
Renaissance: Lancer (no longer anti cavalry)
Industrial/Modern: Light Cavalry (unlocks at railroads, stereotypical Wild West Cavalry)
Information: Helicopter gunship (no longer anti tank, faster movement)
And the heavy cavalry line is basically unchanged (4 movement point, comparable strength to infantry units of the same age):
Ancient/Classical: Horseman
Medieval: Knight
Industrial: Cuirassiers (current cavalry stats, new model)
Modern: Landship
Atomic: Tank
Information: Modern Armour
Anti cavalry functions post pike are handed over to the rifleman who gets +20% against cavalry which otherwise has the same strength as it. The anti-tank gun is now a new upgrade line (as it clearly should be), but I have merged it with the AA-gun into a single battery/field gun unit to make it more attractive to the player. It upgrades to a modified SAM unit called "heat seeking missiles" which retains both anti tank and anti air capabilities. I know that this is an anachronism, but it makes modern infantry units more useful, and helps the AI a lot. Just dump a support unit in the 2nd or 3rd line of your army and you are reasonably well protected.
