I dunno I think I'd be much more interested in a Korean War arena than WWI. We'd still have the Corsair, Mustang (and Twin-Mustang - how cool is that?) and added jets like the Mig-15, Sabre, F9F Panther for CV ops, F-84 Thunderjet and F-80 Shooting Star. The British I believe use the Gloster Meteor and the Hawker Sea Fury. The B-29 and and A-26 were also used.
Not sure what else was on the North Korean side though - La-9 maybe?
Helicopters for downed pilot pickup might be cool.
I think WWI arena proved you need to have more than just a handful of planes that can dogfight only though. To make the arena interesting you gotta have different mission types - strategic bombing, interdiction, interception, ground support, etc.
With such a limited staff though I'd prefer HTC continue to update graphics on its older models and introduce more Japanese fighters, and continue to improve strategy aspects of gameplay.