This comes down to your approach to simming of this kind. Such numbers are daft really. B.A.T. is a campaign makers toolkit. Not really a DGen, or even DCG or generalised thing at all.
The stories told in campaigns often feature the individual's part in massive actions. But from the point of view of a single pilot or crew the action is localised.
I have played great swirling dogfights in Dawn of Flight that had me breathlessly trying to keep up with a swarming nightmare of individual fighters. The fact is there were only 20+ aircraft up at any one time. Sometimes new aircraft appeared later, when I was exhausted and low on ammo. The fights can be huge but not drain resources.
Likewise the Battle of Britain. Your Squadron is a large group, 12 planes altogether. You may intercept 100 to 200 hundred aircraft alongside other squadrons, but in reality you will be close to about 16 to 20. A skilled mission designer can keep you very busy, work you to death with overwhelming odds, and yet never have more than 32 aircraft up at any one time.
Smart missions, smart effects, the individual experience is detailed, super detailed, and the action around you does not actually exist until you are part of it, Heisenberg like, in your own scripted reality.
The generalised approach, everything stripped down for performance, bare airfields, limited models, fewer effects, less demand on the sim for the specific in favour of the general. Sorry, that's not my bag.
Performance comes down to one or two great airplanes and as many enemies as you can personally handle, 3 or 4? B.A.T. is not designed to throw 400 robot airplanes into a blank arena. One Ace pilot can kill you just as quickly.
Instead, B.A.T. will illustrate some of the very best flight stories. I know some of the people who were part of those stories and I know some of the people writing them...