Numbers... but beyond that I think it's a matter of familiarity. It's hard to let go of the MA.
But the numbers have to be dealt with, and this is probably the purpose of this thread. To get the numbers up...
OFFER WHAT THE MA CAN'T.
Number 1, do away with base capture... at least not all the bases if you can differentiate. Or just make the bases destructable with longer regen times.
I like the limited plane set part. Maybe one side gets better planes, but it does provide variety and forces me to try new rides. I won't mind ever seeing another LA7, Tiffy, Tempest or P51 as long as I live! But many don't agree with me so offer variety.
Encourage side switching to even the odds. It's no fun being mercilessly ganged all the time. Two sides is best... easier to keep balanced.
If some want to milk run, let them... they can get their jollies and aren't hurting anyone if base capture is off.
Sunday night my squad went to the CT to escape the Desert Terrain and land grabbing hordes. Everyone had a good time. I think we will do it more often.