If I had a crack at it. Id take a 3 track approach. 1, take the total sum of all the current and past codex and make base rules and stats for all air and void craft in the 40k universe.
Track 2 would be to do the same for 30k and make narrative campains for the Horus Heresy and the Emperors Great Crusade.
Track 3 would be to tie in AI with elements of 40k, epic and bfg. Im not saying have all models and rules fully represented as that would take forever to do a game turn. but have your air battles able to influence what happens on ground or in space between fleets.
One of my favorite appocolips games I played between Chaos World eaters/Necron vs Tau in 40k was followed by a AI campain where we reenacted the bombing runs each force did for the 40k game. It worked out well and was a thrill to play out.
With those three things done then Id start commissioning the models to be made, even mabey a contest to the fans to submit a entry that would be made a official FW model ( either as is or the concept to be cleaned up by a profesional model maker).
Now, what would you do??
