After intensely studying AI vs AI combat I have these suggestions. This is not meant to "Improve" AI as much as make it more functional.

AI Jetpacking Fix: Allow AI controled units (friendly and enemy) to have unlimited jetpack fuel. Ive noticed pathfinding allows AI controlled mobs fall into holes and become stuck very easily so this should fix the problem. (Please note that jetpack fuel would have to return to normal as soon as a player assumes control of said Mob)

Return Fire: This may require some AI modding but would help tremendously in AI combat. When a Mob is shot the AI should instantly target and shoot at the mob firing at him. If the mob is outside of range it should pray and spray one full clip of their equiped weapon in the direction of the attacker.

Unarmed Man: When a mob is unarmed it should immediately pick up a weapon that is nearby. The Ai used to do this already but ever since build 26 it stopped. (Im refering to the start of each skirmish you have to manualy equip all weapons)

Mining: When you input a goto command and its underground if the mob has a Digger equiped it should dig its way to said goto point. (Probably realy tricky to do but if anyone can pull it off hey go for it)

Crouched Mode: Think sentry mode but crouched.

Sentry mode: All mobs should start in sentry mode at the start of each game

Umm ya thats it! Im no modder soo im not sure if what im requesting is impossible so im sorry in advance. If you could do any of these suggestions that would be great, me and my friends play this on a bigscreen and this is our wishlist.

Interesting post,
I would like to drop my 2cents:
About infinite jetpack fuel for ai, I think it is a understandable argument, but it can be exploited to reach "unreachable" places,no? What about doubling fuel for ai?
Return fire: i agree, but ai could valuate chances to hit target, and maybe choosing to: retreat, drop to ground,charge or just fire.