That's some real complex coding, however.
Not as bad as you probably think. You could use a variant that Deathcam stuff that MadVader / I wrote, where the camera gets placed somewhere high, then is tied to the XY position of the airship. Steer the airship with WASD / arrows, have keys that cause firing events to happen, then do some simulation mechanics. The only really hard thing is setting up damage to the airships and the weapons, but IIRC, projectiles can already check for collision with objects, and the rest of it's basic gamecode, other than providing a presentation that showed the health of the airships involved.
IOW, pretty sure all of that can be done, and the Mirage cannons would still be an option, as would going straight to boarding. Personally, I think that instead of the Mirage cannons, you should fight the enemy, and if they're "shot down", then you can have a battle where your forces "land" and the enemy fights you from the wreckage. Or you could board them and possibly take their airship intact as a mega-loot item. That would give players interesting choices. In the same vein, you could either "invade" an enemy fortress by landing airships nearby and have the armies assault it, or drop troops wearing DaVinci gliders (ok, that
would be a royal pain to code, but whatever).
Anyhow, just ideas. It would really bother me to play a game where I couldn't shoot the airships down, and it'd be epic if it was something that was more interesting than a menu option.