I just though of a great idea: units based on the four special materias. There will be a warrior, a swordsman, a guerilla, and a marine for each materia, each with better stats than the last (of course), and each group of four units has special attributes, For example, a HP<-->MP Warrior costs twice as much as a regular warrior, but has 5 extra HP points. A Mime Warrior also costs twice as much as a regular, but has as many possible abilities/attributes as possible. And then the units upgrade in the before mentioned units. The reason for their uniqueness is because of the rarity of the materias (there's only supposed to be one of each).
I also made some other improvements, such as making the Gross Panzer cost a lot more, since it was a combination of Mech Infantry and Modern Armor (great offense and defense), while making it a Flag Unit for Shinra to build it.
Right now I'm working on some Civlopedia/PediaIcons editing, along with creating the mentioned units.
EDIT: Here is the city list for the four civs:
Shinra:
Midgar
Junon Harbor
Kalm
Costa Del Sol
North Corel
Rocket Town
Mt. Nibel
Icicle Inn
Mideel
Mythril Mines
Bone Village
Gold Saucer
Gongaga
Crater
AVALANCHE:
Fort Condor
Cosmo Canyon
Chocobo Ranch
Lucrecia's Cave
Nibelheim
Weapons Seller
Chocobo Sage
Sleeping Man
Cactuar Island
Ancient Forest
Goblin Forest
Frog Forest
Wutai:
Wutai
Da Chao Monument
Cetra:
Temple of the Ancients
Forgotten Capital
The materia caves are barbarian-owned (so they're up for grabs if you want the special units), along with the Chocobo tracks. And don't worry about the barbarians, they're set on the least aggressive mode, so they're pretty much just for show.
Tell me if I should change/add cities, please.
And on another note, here are some hints/tips/thigns to note when starting/playing the game (after I finish it):
-Make sure, no matter what difficulty you play on, that you build a defensive (or any unit for that matter) unit to fortify in each of your cities, along with the Walls improvement. This is because Shinra will probably be constantly bombarding you with attacks.
-Make lots of good trades with your allies to make sure they too can put up a fight.
-The marsh is a very dangerous place (gave it disease rating of 100), so try not to build cities near it, nor do any work on it.
-I gave all terrains stats of (3,2,2), (2,3,2), and (2,2,3) depending on what the terrain was, in order to give a fair chance to all cities, to not take long to reach the end of the tech tree.
-I made some units upgrade that normally don't upgrade due to taking up space on the city list of possible units/improvements and their obsoleteness later on. Some examples are cavalry upgrading to tanks, submarines upgrading to nuclear submarines (nuclear has same stuff as regular, but with better stats, so why not), privateers upgrading to submarines (after giving submarines "Hidden Nationality"), Bombers upgrading to Stealth Bombers, Jet Fighters upgrading to Stealth Fighters, and some other ones I can't recall.
-Airplanes can actually move now (not Immobile anymore), due to the fact that the Highwind is obviously not Immobile, and movement is determined by age of aircraft and potential speed (in real life).
I'll post more stuff when I release it, or when it comes to mind.