I'd agree with SEA being more fun that the LW arenas often enough.
And it has far better maps and tiles available. Scenarios are fun, draw a good crowd, but are infrequent. KoTH has been getting nice turnouts twice a month. Not sure about the air races, and I haven't been on FSO since the early break up of LCA last year. Wed and Thursday Snapshots have a mixed attendance.... I've been in a few with maybe a dozen to two dozen players in the arena, but usually still a lot of fun.
As a percentage of the overall player base, even SEA numbers are small compared to the combined LW arenas 24/7. But, yes, SEA attendance is far above EW, MW, and AvA.... just not quite up to both LW yet.
I could see and welcome the addition of planes to support SEA, if the planes will draw fliers.
For example, Snapshot Tigers Over Rangoon has P40's vs Zeke's. Now the Axis are supposed to the have the numbers over the Allies in that one, but usually the best you can do is a 50/50 split and switch plane-sets for frame 2.
Now, switch those Zekes for the more historical Oscar, and you will have a very difficult time finding players that will want to fly that underarmed, less rugged Japanese Army fighter against the P40's. Especially since with the Oscar, the original 60% axis / 40% allies split becomes more crucial to game balance.
More historical? Yes? Will it get used? Probably not much. Does it help the snapshot event? Probably will see a few players actually leave the event and you'll not be able to get a balanced 60/40 split for the snapshot.
OTOH, adding P-39's and Pe-2's to the Russian plane-set in a Russian front SEA event to complement La-5's, IL-2's, and Yak's would probably work in the SEA as well as finding users in the EW, MW, and LW arenas.
I'm not opposed to EW additions, so long as they are competitive for use in the game in more than one special scenario.