Make the "second" arena a 150X150 kilometer square of Central Flanders, with Arras and Cambrai near the center, with the late 1917 no-man's land doing it's sweeping "S" turn down the middle. You can have most of the airfields that were historically significant close to the front, and yet have room on the edges for bomber/obs squad airfields for those that like to take the long scenic route to their targets. You've got the Somme valley to the south, and Vimy Ridge and Lille to the North. It's fairly accurate historically, and it's got enough windiness to the front that it doesn't get too boring.
Just as a reminder, Most observation balloon stations were operated somewhat back from the front about 5 to 10 kilometers. One also needs to remember that the prevailing wind on the Western front was predominately from the West and favored the Germans, who flew mainly an aggressive defensive strategy. There were never any Allied airfield raids made by German Fighter Squads, and there were fairly little Entente initiated, German airfield attacks.
If any of you remember playing RedBaron3D, the quickest way to loose most of your mission's squad mates was to do an airfield strafe and low level bombing. The MG nests and Flack will murder most of the squad.
