Jackal, the limitations which force people into flying a particular style, is already in the game. ENYs, OBJs, perk points - these are all external devices which its original purpose was to provide incentives or burdens to balance the arena out in plane usage.
It's a matter of function, not of principle. "Free choice" is limited upto the point it does not disturb the overall balance of the game.
Ofcourse, whether the current status of the MA is truly unbalanced or not.. is something else to talk about.
...
One thing for certain is that of some 60+ available planes in the game, only a handful are ever used. The rest remain hangar queens - a choice for those who indulge in sadistic delight.
Its quite obvious that the planes of the earliest WW2 period would not survive in an all-out slugfest like in the MA.. but there are still about some 30 "midwar planes" which has good potential to see major MA use - if, the right conditions are met. More planes to ride in, more planes to fight against, more variety of situations, and more roles to be diversified.
If that does not mean more fun, then I don't know what does.
Ofcourse, limitations mean that some people who indulge at their present choice of planes might not be able to do so once new rules are set. But like everything else, you can't have it both ways. We already have Spit14s, 262s, Tempests, F4U-4s and etc etc.. which could always be someone's favorite, that are out of reach for common use, due to penalizingly high perk prices. A lot of RAF fans in AH feel unjustly penalized, because BOTH of their favorite "ultimate late-war fighter" is perked at ridiculously high prices, while all of the other country's "ultimate late-war fighters" are totally free... all in the name of "balance".
Balance is a delicate thing to consider, and when someone changes that balance, many people will be happy, many others will be angry - until the changed balance comes to be accepted as the new standard over time.
The only real question is would that change benefit the MA ultimately?
IMO, it would.