Honestly, Fill out the planeset.
The limited one we have now doesn't really allow that great a(n) EW or MW experience, IMO.
And then, limit some of those rides to those arena's. For example, Put in a Gloster Gladiator, and a Fiat CR.42, and only enable them in EW. If that's the only place you can go for a nice little Biplane furball, then you'll see more people in there...In theory, of course.