First off, this mod is absolutley amazing! At the time of writing this I've only messed around with the Hunter Chopper, and I can say that it's incredibly well detailed and fun to use.
Before this mod existed, the only way to fly a Hunter Chopper was with the Parakeet's Pill Pack, which physically turned your character into a chopper. This version had no first-person, no tail rotor movement (nice detail by the way), no crash animation, no carpet bombing option, etc. This mod fixed all of those nagging features that the Parakeet's Pill Pack was missing when it came to Half-Life 2 vehicles, and is more polished, fluid, detailed, and overall more fun than any previous Half-Life 2 vehicle mod before it.

I'd like to see some little things added here and there, but the overall mod is fine as it is. Firstly, I feel that a siren should be added to the Hunter Chopper's carpet bombing feature when the player switches to it. I believe the sound file is called npc/attack_helicopter/aheli_megabomb_siren1.wav; it plays when the chopper in your mod has sustained heavy damage, and is on the peak of crashing. I'd also like to maybe see a stationary rotor model added to the chopper and the Gunship as well, but I know that that's probably asking too much since modeling is fairly complicated.

I may add more ideas to this thread overtime, but overall I feel the mod is excellent where it stands. Keep up the good work.