I like MW, it's planeset is a nice balance.
I'm confused about why we need to eliminate them anyways? How does their existence hurt your gameplay in any way?
I would enjoy Mid War and Early War MORE if it were truly a different experience. As it is now, it is just limited plane sets and lower numbers. Maybe a compromise: Early and Mid War Axis versus Allies arenas going a step further, to pit same period rides from
different sides against each other. Maybe a better question is what do these Arenas add, and can they be improved?
Anaxogoras said it better, I am thinking of the "theater-based" arena division as a more appealing split. With the exclusion of fleets (as we know them) in one arena, there will be a choice for those who either want to fly in a somewhat more classical European planeset. And with the exclusion of Luftwaffe (except for maybe some filler replacements) their will be a choice to fly in more classical Naval battles over flying your favorite ride.
Right now, the choice for Late War is based on #1 number of players, #2 number of friends in that arena, #3 the map itself. All three of these are trumped at any given time, by an arena cap

, so not even a choice in that case.