Certain actors should be significantly more vulnerable against certain types of weapons, but more resistant against other types of weapons, to add more strategy and depth to the gameplay.
I also think that the expendable drop crate should look more like a re-entry capable capsule, with retrorockets to cushion the impact, then breaking apart and releasing the contents.
And, as said before, dropships and rockets shoud be a more valuable resource.

Grasslands needs to be redone, AI doesn't fare too well in it and it is too small/weird.

I'm pretty sure most if not all of these have been posted by someone else already.

Easily changeable (I have looked at these and I think I know how to change these)
-Homing rocket launcher needs to have a faster initial velocity. (Make it a Javelin missile launcher looking thing?)
-Make the Heavy brain bot skinnier and shorter.. He can't crawl or travel through bases. The head scrapes on the ceiling. (It may help to make the brain smaller?)
-Uber cannon reload time should be changed. Clip capacity, I think that ONE IS ENOUGH. (you can change the gibs if think the explosion is not strong enough.)
-I dunno what the trade star frag shell is for.
-I can't throw grenades accurately. therefore the one grenade system is not fit for me. (I saw an earlier post. reload time or clip capacity maybe?)

Complex things (I have no Idea how to change these. Possibly LUA?)(note that LUA can do a lot but it can't do everything.)
-Flak cannon (Coalition) should have a proximity fuze. I keep having the rounds blow up quite a bit ahead of the target, or the round hits the target and sprays shrapnel everywhere. Including at the firer.
-RPC bounces. Sort of WTF?
-materials/digger balance. Metal is weak. (and also debris. rockets can crash at high speeds into the ground and barely create any wreckage.)

Things that need changing but do not belong in this thread.
-a few more campaign maps?
-better scene editor (or was it map editor?)
-AI is weird. Suicidal brain bots, friendly fire, Jetpackers etc. some guy landed between two of my coalition light soldiers with ARs. one of my guys killed him, but the other guy gunned his ally down AFTER THE ENEMY WAS DEAD. Also, some coalition light soldier jetpacked over my heavy brain bot as fast as a bullet while firing an AR on full auto. about 70% of the shots hit me.

I agree with the AI needing some more attention. Preferably their walkpaths and stuff since they crouch while going upstairs, making it more impossible to get up them.

I also dislike (probably numgum's fault JUSSAYIN) the vanilla weapons and their balance... I almost prefer somewhat underpowered weapons since you really needed to use tactics at that point. Long arsed reload times are not the way to go, figure somethin else out.