I haven't read every post but my observation is that not all P-51D drivers are carrying ord. At the same time those that aren't are rarely flying alone. When I run into them there are 2, 3, 4, 5 or more and they are willing to fight my Spit. I say God bless them. They've at least gotten beyond fighting buildings. I've fought many multi Pony groups. It's often a chess match and it's fun.
The P-51 (along with the Spit) was probably the most iconic fighter aircraft of WWII. Sorry other fighter supporters; the Zekes, 109's and 190's are close seconds but lets face it; when you think of WWII these birds are most commonly mentioned. To try to limit it's use in the game is futile no matter how you attempt it.
I will say this... after reading the beginning of this thread I'm considering parking my Spits, 109's and 190's and spending some time in a D Pony. My brothers would be proud. One built a (very large) RC of Cripes A Mighty and the other chastises me regularly for not flying American planes in the game.