This is a Catch-22, you can get what you want with a custom arena but, even the best meaning players have been more willing to show up in the standard play arenas than custom arenas. If you are getting a turn out for your weekly event in the WW1 arena, don't mess with a good thing. If the players doing these things are not part of your regulars, it would only take once for all of you to switch sides and entertain your greifers. A positive thing could always be the next week they would bring friends to take all of you on.
I'm going to venture since the airfields no longer have auto ack, allowing rear gunning from a park aircraft is a compromise. The wish last year to disable that appears to have gone nowhere.