Rolling plane set will drive away players if they don't have access to the planes they want to fly. It didn't work for WB and one of the main reasons why I left that game. It sucked having to wait 2 week to fly the P-38F and then an additional week if I wanted to fly the J model and had to wait until almost the end of the campaign to fly the L model.
Well it could be the same like there is with the 163 and 262 currently.... once you get enough points you can fly your plane before its 'release' date.
And not to make it super hard or frustrating, once you get enough points, you get for example 4 uses of that plane. If you get back to base you don't loose any uses, but if you die you get one plane less.
This way you would have to make lets say 1 sortie with kills with the 'base' plane of the current year to have a higher tier plane, 3-4 sorties for even higher tier etc. This would have people fly early and mid planes.
So have all planes possible to fly by accumulating enough points, and have them gradually being introduced by the time of year.
Everyone is happy = more players = HTC is happy
This isn't a WW2 flight sim, the core game in no way tries to simulate or replicate WW2.
Ugh i might be missing something, but this is from the front page of the website
'Welcome to the best WW2 combat experience online'