Hello Starke von Oben, it's been a while since my last visit to this Forum but I'm glad to see more players like to tinker with their .txt and .gif files!
Here's what I did to the rules.txt file (and modified my units.gif file to suit) :
1. The cost of city improvements is now in multiples of 40; this is because 40 is divisible by 3, 4, 5, 6, 7, 8, 10, 14, 15...
2. The cost of military units is now in multiples of 20; except for plain warriors (10) phalanx and pikemen cost 20, horsemen 20, musketeers cost 30, all other mounted cost 40 (60 for modern cavalry, 80 for all armor)
3. The cost of ships is 40, from trireme through caravel/galleon/ to frigate; ironnclad is 60, all others increase by 20 every tech improvement.
4. Movement and ZOC: caravans/trucks ignore ZOC; diplomats, explorers and spy are all in the same "ignore ZOC + diplomat" regimen, all cost 30, the real difference being movement (diplomat move 2, explorer move 3, spy move 3x road i.e. forever)
5. I have invented the following units: extra land = minefields (req. explosives, cost 20, move 1); extra sea = seamines (req. explosives, cost 20, move 1); extra air = hot air balloon (rep. physics, cost 40, carry 1, move 3, ignore ZOC)
At which point, if you flag not only paratroops but settlers/engineers as air transportable, you can airlift settlers to colonize that sweet spot the AI enemy ships are blocking, and disband the baloon to create a instant phalanx/pikemen for immediate defense
6. For all my efforts, there is no way I can shoot with land artillery against a ship hugging the coastline, so I am experimenting with a military unit called "coastal fortress" so I can not only defend my harbor (there is a city improvement by that name) but also "shoot first"; now a coastal fortress is fixed, but if you don't allow at elast "1 square move" you can't shoot at enemy ships; the problem is the AI is likely to create coastal fortresses and send them off to sea...
7. On the other hand, I find it absurd that a seagoing vessel may attack a land unit (i.e. trireme vs. horsemen), not kill it and be sunk by failure...
8. I have edited the cost of some Wonders, mostly NOT making some obsolete through time but keeping them forever (i.e. Pyramids, if they're silos for grain, they're there forever; same for the Oracle or the Hanging Gardens)
9. I do not enjoy playing with the most recent technologies, so I have not tinkered with electronics/laser etc.; however I do believe that the "Manhattan Project" was engineered in the wrong way, i.e. the one to complete such a wonder should become the ONLY nuclear superpower in the game, rather than giving away the secrets of nuclear weapons for all to use!!!
10. After Temples the Coliseum and the Cathedral, no more entertainment city improvements? Discotheque, anyone? Golf courses, baseball diamonds, theme parks? Disneyland???
I'm going by memory so I may have forgotten something