I've always been a huge fan of strategy games. I've been a player of Dune II, Red Alert II, Warcraft II, Age of Empire II, Civ II & III, Starcraft, and possibly others.
Originally, opposing sides had either units that were more or less exactly the same, or at least units that looked different but were functionally identical. Then the makers decided to change it up, make the strategy a little asymmetrical and give the various sides different sorts of units. Starcraft even made the means of production slightly different. One very major aspect has always been the same though: the economics.
Invariably, one must harvest something in order to produce your tanks. It is odd to me that this should be the unexceptional rule, since throughout history only Columbian narcoterrorists have really had such a direct corrolation between production and military output. Normally, the military strategists have a set budget. Yes they have to fight fluctuations of it in Congress, but dear god don't make THAT part of the game. Not only is it unrealistic, I find it incredibly annoying, as keeping an eye on my workers and balancing production between economic capital and military units is not what I play strategy games to do.
In addition your vehicles will have a build cost but no maintenance cost. This allows one to simply continue to build up bigger and bigger armies over time. This is also very unrealistic, as the limit to military build-up on a strategic scale has always been available support budget, not build time. For example, I would imagine the "cost" of an infantryman is somewhere near half the yearly cost to maintain him anyway, or such (since what you're paying for is primarily just paying him during training). So you see, this is not only unrealistic, but also effects the strategic interplay of the game.
I think it would be interesting to make a strategy game that not only breaks from the standard harvest-based economics, but has the various factions work on different economic models. Here is what I thought up:
Democracy: The military forces of a democracy will have a set budget. However, for every person they lose (counting both infantry units and members of vehicle crews), they lose some of their budget (as popular support for the war goes down). Consequently the Democracy forces will want to emphasize stand-off attack weapons and expensive technology that will minimize losses.
Communism: Communist forces will have a set budget. It doesn't matter how good you do, the budget comes from those who produce in accordance with ability, to those who need in accordance with need. In fact, your budget might even go DOWN if you're doing well in the scenario. Purchase of additional units, however, isn't done by paying a set price, but rather requesting the units from central command, whom will decide whether or not you really need the unit, and send it to you with substantial delay. (= Units are cheap, however, and maintenance costs, especially personnel pay, is low. Available units are quite technologically advanced for their costs.
Local Warlord Kleptocracy: Budget depends on holding on to certain key stratego-economic points. Also, likely funded by a Democratic or Communist force by proxy (this money will probably just be a set amount). Kleptocratic forces will probably use cheap out-of-date predecessors of Democratic/Communist units, and technicals, and such.
Insurgents: My main thought with insurgents is that whereas other factions will have structures and vehicles, as is usual in strategy games, the insurgents will have primarily only personnel units. For example more units will be recruited by a "recruiter" individual, whereas for most other forces they'd come from barracks and such. There will be some buildings however, such as weapons caches and bomb factories. The basic idea is that most insurgent units will only be detectable up close so they'll be hard to find. I'm not sure how they'll be funded. I'm thinking they'll get a certain bounty for killing enemy forces, and perhaps budget increases when the enemy accidently kills civilians. ...and maybe a small permanent budget to tide them over - this is the money Iran is giving them ;)
Narco-Terrorists: Think FARC-EP. They'll be the only ones to work like most stategy games -- budget will come directly from operating and harvesting hidden drug fields and labs.
Mercenaries: The Mercenaries work for whomever and are entirely funded via bounties on destroyinig enemy units.
And of course, as I noted above, maintenance costs should be such that the size of your forces is limited by the budget, and can't grow ad infinitem until you can zerg rush your enemies with mammoth tanks. You'll have to actually utilize tactics and strategy to destroy your enemy!
So there you are. I think someone should make this game.