I'd agree with adding strats to a specific aircraft, the P-51 wouldn't be one of those aircraft, however.
Not trying to hijack the thread, I do think some type of system that you need to progress through to unlock certain planes, or limiting some of the lower ENY aircraft would be a good. The problem with this is it may discourage the "casual gamer" into playing, as it would take longer for them to make certain things accessible.
How or what that system would be, I have no clue. It doesn't pay for me to think.