Oh. That would be difficult over and above the objection to AI in the MA (I am one of those against it in the MA). You would have to create an equal number of AI defenders against the mission in one or both opposing countries. A lot of moving parts. Posted this before I saw your edit
For instance, in the missions I helped Nefarious build for his Fortress Europe events sound very similar to what you'd be doing. If I recall it was a large bomber formation that followed a route to a target dropped and tried to return to a base.
There were no AI fighters either side.
There were no AI units defined for the other faction at all. Single sided mission.
Large AI bomber group formations. Nefarious would populate some of the bombers with players the rest were AI driven.
If a player's bomber was shot down during the mission, Nef could re-slot them to an available AI bomber and the player would take over as PIC.
Walk-on players could join the mission even if they had missed the original launch. Nef could slot them into an AI bomber in flight.
If Nef doesn't have copies of those FE missions they are still in the DB I assume and I'm sure HT could extract them for you. They are just marked to not show up i the normal mission listings by default.
I had also created multiple large bomber formation templates he could easily import and start with to save a lot of work. Hopefully he still has those formation templates or else you could extract them from one of the FE missions. There were both Allied and Axis formations that were historical to the best we were able to find info on at the time.
The basic idea behind FE if you never played one is a large AI\human bomber group gets spawned from a starting point. Human bomber pilots could either be slotted into that formation or just spawn a 3 group independently and tag along. (Note: the AI bombers were singletons. AI didn't support 3 groups so slotting a human into one gives him a single bomber. )
Human escort pilots spawned near by in fighters and escorted the AI\human formation and tried to keep as many alive as possible.
Human interceptor pilots spawned and flew to shoot the AI\human bombers down before reaching target and then keep as many from reaching home as possible. I think he had some kind of scoring system based how many made it to drop and how many made it home.
The AI just become a rolling target to focus the activity in a certain area. The action is going to tend to seek and stick to the area around the formation creating a localized rolling furball on the move. the AI bomber formations were focus point for the fighting to be pulled to like gravity.
I think if they had continued they needed to be whittled down in scale. We wanted to start over the top to find the edge condition and start pruning back to find the optimal point for performance. Not sure were he stopped at.
But those sound a lot like what was being discussed. I think most participants had a lot of fun on those.
$0.02.