Reading Acegirls comment (excellent one) something came to mind...
If the servers show what year of the 'Great War' the game has chosen, you have to pick a plane of that period.
We would have to have a plane for every period we want to play in.......hence the money problem is solved.
(I don't know about you guys 'n girls, but I only got the best planes, and skipped the rest, or never use them again......terrible waste of game assets!)
It will be more fair to all players, cause only skill will keep you alive ( not just 'best plane wins').
If one chooses to fly in a dated plane against better ones, he should be awarded more points. After all the older planes were still used, as reconnaisance planes, or to shoot down observation balloons, against ground targets, or used in distant outposts and parts of the front of less strategic value.
They might have such a mission, like "find enemy tank batallion and mark the target". You can sneak in and out against much better planes and still be the hero on the day (and not be just target practice!).
Then the game can progress into the 'antebellum', the time between the word wars, but with other conflicts, and newer and better planes can be added.......
An endless persuit of happiness!
The sky will be the limit!
Yey Dogfight! (.......oh! Sorry, I get carried away!.... 'NO! Not the padded room!')