Before my computer died I had been searching the internet for info on spawning npc's and getting them to do stuff. I'll post what I have found out on here when I'm done. You can control some ai (make them move places). Only small things at the moment, not helicopters and st6riders, BUT IT CAN BE DONE.

Cool, I would really like to have an army of striders following me (helpers).

Yes I know. I have been able to control striders that have been created by the game itself (as long as they don't follow a path. This is usually from fan-made maps where they just put in a strider without getting it to do anything). It is cool, (although they still attack you). There is a way to control how an ai attacks (secondary or primary) and where it attacks (co-ordinates or selecting an ai to be attacked) although it is really complicated. Controlling manhacks is also fun. They can't shoot and the things they run into get hurt. Turn manhacks on their combine allies!
I'll post a guide on doing all this in the future. 8)

Cool. Isn't there some sort of mod that allows you to become the strider or whatever?

Yeah, it's called the strider mod. But that's where you drive it, not where you have em as pets (or even better, mindless slaves to do your bidding! BWAH HAHAHAHAA). 8)