HTC stated they wanted it to be a pure dogfighting arena. Still a valid concept but with just four planes to "experience" the whole concept has very short legs.
I would think that a WW1 "Main Arena" style approach would be far more entertaining in the long haul.
Well HTC has started down other approaches in the past (e.g. Night flying, Field capture order, etc) that with the help of player "feedback" they were able to realize needed to be reconsidered.

With respect, I would assert that merely adding more planes to the one-dimensional gameplay of a dogfight only arena would not materially improve its attractiveness to the larger potential audience. Keep in mind, the DA furball lake offers almost the entire planeset of the WWII MA available unperked. Yet, while is has a small following, its popularity is dwarfed by the MA. It must not be the planeset. I assert the MA provides a richer gaming experience with a wide variety of task, missions, and GOALS.
Goal-Oriented-Combat is the key to generating that special addictiveness that keeps people up to 4am in the MA. Otherwise, its just practicing.
Once you have that...of course, new planes are always welcomed.

Regards,
Wab