That is the sort of thing you might find in a munitions dump, and it does not need much training or other equipment besides breaking any launch encryption it may have. Without this unit, gunships could dominate the game.
Sorry, but that isn't true. SAMs take a lot of training. However, like you say, if you are using them to merely shoot at helicopters, then it would be easier. The problem is with SAMs is that it's very hard to train for them since you pretty much have to use the weapon in training which sort of defeats the purpose. Plus, if most of the helicopters are more of the "Road Warrior" gyrocopters, many SAMs would have trouble locking on due to the close range and lack of large, jet-induced heat signature. Plus, SAMs aren't very common these days. The Army is sort of moving away from those units since the threat really isn't there and we need the troops for other missions and we haven't had US troops attacked by enemy air since Korea.
What I think you are thinking of is throw-away anti-tank weapons such as the AT-4 which have instructions right on the weapon.
However, my view is that if you have enough helicopters in the game to be a problem, it implies a level of technology that would make relying on found weapons moot.
That being said, let me just point out something that often times civilians miss: developing a technology is very different from 'weaponizing' it. For example, building the little helicopter you see in "The Road Warrior" probably isn't hard at all. However, besides manually dropping bombs, turning it into something resembling a gunship is another matter entirely. So yes, you could have lots of ultra-lights and small gyro-copters, but they really wouldn't be affective combat units. I mean a competent shop mechanic can make a AK-47 by hand (and they do in Pakistan, I got to see one while I was deployed to Afghanistan) but it's another thing entirely to develop a gun system like for a WW II fighter. Hell, I'm betting that unless you happened to find a very technical book, it might take some time to develop the arresting gear they used on WW I fighters.
I guess the AI would use land transport as stupidly as it uses naval transport, then. When you've pointed this out on other forums and there was no response, I guess the only possible response is, "You're right, it's stupid". Rewriting the AI on that fundamental a level seems impossible unless the Firaxis devs do it.
The whole AI thing was one of the only disappointments I had with Civ IV. It reminds me of the issue with word processor spell/grammer checkers which actually seem to be getting worse with every new iteration.
BTW, in any of your research for this game come up with anything on the chemical side of things? I ask this since I wonder how easy/hard it would be if things suddenly fell about to make gunpowder. I mean, how hard would it get be to get sulpher? Or is there a 'easy' chemical trick that most people who took a college chemistry class would know that could make it? I ask because if it would be hard to synthesize, then perhaps you need to have sulphur as resource which I think would be really important. Sure at first you can cannibalize stuff, but after a decade, you'd think you'd have stripped everything pretty clean and any civ would be desperate for gunpowder.