Having means for the community to improve the AI would be really, really great. Most sims, especially in recent times, have pretty much neglected the AI area compared to features like flight modelling, graphics or multiplayer. Which is a shame because good AI is fundamental to a realistic combat experience.
Now everyone knows that AI programming is a complex topic, but in many sims it already fails in basic decision making, which is not
always that complicated: not entering combat when the enemy has three times more planes, not chasing an enemy over his frontline when low on fuel, abandoning a bomb run when enemy AAA has not been destroyed by SEAD aircraft... you just don't get this logic in most sims
If you find a way to provide event handlers for most situations and scripting possibilities to influence what the AI units should do under which conditions, that would be incredible!