I've tried out a lot of different planes in dogfights with the AI, and have come to this conclusion. Most of what constitutes the aggressive 'AI' seems to be an Aimbot of sorts. In fact the aircraft's whole behavior seems to revolve around it. I'd go so far as to say it is programmed more like a guided missile than an enemy pilot (it'll even collide the plane into you if it gets the chance to).

 My issue is that it often makes dogfighting unfun. You often have to keep it at a high altitude to ensure the enemy doesn't crash in the middle of the fight due to minimal if any terrain avoidance. Though I've seen it turn away from the ocean floor at least once, it seems to take the idea of avoiding a crash as a suggestion. 

  It can be somewhat fun if you're using a similar performance aircraft to them, but if they have the turn rate advantage they're likely to glue to your tail. Basically meaning if you aren't turning constantly the enemy will just shot you down. If you have a massive speed advantage it's all but certain it'll head on with you.  

 The ultimate problem is that the aircraft is constantly fixed on aiming and shooting at you, with not even a basic sense of self preservation. It never tries really tries to avoid being shot at, with the only defense it seems to know is shooting flares. 

 As for what the mod could have. One thing I would suggest is giving the AI the ability to read the aim of your guns/missile lock circle to some extent. It is capable of reading its own aim, as it has shown to be surprisingly good (though not perfect) at leading shots. 

 I suggest having it read your aim so that it can chose to avoid the aim of your guns/missile lock radius. This could make help prevent the AI from doing nothing but head-ons, as it's detection of your aim will encourage it to turn away. 

 Implementing a 'defensive mode' that activates upon a detecting the player's aim upon it would probably be the best way to use this. This mode would have it either attempt to avoid the player's aim, or if it can't, attempt the option of 'running' and using speed to escape (and vice versa if it can't run). Maybe even give it a last ditch tactic of cutting to 50 or even 0% throttle to try and make you overshoot if all else fails.

 Another thing that would be good would be some form of 'anti-crash' program. Make it try to avoid mountains, the ground/sea, as well as you if it gets too close. I would suggest simply having it simply be programmed to 'pull up' if it comes near the ground/sea/terrain/player aircraft. It seemingly does that to come extent for ground/sea, but expanding on this seems like a good idea. 

 Despite the long post I am trying to pitch an idea that would be the simplest to program, not asking for something highly advanced but some a few additions to make the AI seem more like a pilot and less like a guided missile.

 The addition of 'Allied' AI would also be a nice addition to such a mod, AI that will attack aggressive planes and planes that you shoot at.