I'm failing to understand the need for a ww1 arena to test an expanded damage model. If they want to do a new era with new planes then fine but what's stopping them from just making planes compatible with the current plane set with an expanded damage model? I don't see the causal relationship.
Probably because testing within a WW1 arena takes more variables out of the damage equation, and lets them see how their "experimental" damage model is handling things. In the regular plane set there is a large variance of performance by the ordinance, from small caliber machine guns to extremely large cannon, let alone plane performance envelopes.
One would probably try to remove those variables and see how the model handles very similar rounds on different planes that don't have huge speed differentials, such as a WW1 arena. Just a scientist's view, mind you.
I still think this new endeavor is someone's stubborn pipe dream. I have to admit, I'm skeptical on this. But, again, if it makes the game better for some and brings new subscriptions, that's great.