Personally, as being a self proclaimed 51 pilot, I'd rather just see the just the RAF Mustang I (2 .50s and 4 .30) with an Allison powerplant, the Mustang II (Allison powerplant w/ improved supercharger).
Specifications
Model - Mustang I
Production - 620
Length - 32.25
Height - 12.2
Wingspan - 37.04
Weight - empty - 6536
Weight - normal T.O. - 8600
Weight - max G.W. - 10,600
Powerplant - Allison V-1710-39
Horsepower - 1,150
Propeller - Curtiss 3-bladed electric 10'6"
Max Speed - 388 @ 15k
Service Ceiling - 30,800
Fuel Capacity - 180
Drop Tanks - na
Range - 750
Guns - 2x .50 cal, 4x .30 cal
Bomb / Rockets - na
Also the standard A-36 Apache would be great, considering the theaters of service it particpated in.
Specifications
Model - A-36
Production - 500
Length - 32.25
Height - 12.2
Wingspan - 37.04
Weight - empty - 6087
Weight - normal T.O. - 8600
Weight - max G.W. - 10,700
Powerplant - Allison V-1710-87
Horsepower - 1325
Propeller - Curtiss 3-bladed electric 10'9"
Max Speed - 356 @ 5k
Service Ceiling - 25,100
Fuel Capacity - 180
Drop Tanks - 2x 75 gal
Range - 750 / 1375+
Guns - 6x .50 cal
Bomb / Rockets - 2x 500 lb bombs
I've often wondered why the Mustangs didnt have the multiple variants in AH like the 109 series or the Spit Series. Looking at the generla shape of the planes, I dont think it would be overly hard for the talents of HTC to incorporate. So bring in more Mustangs, but leave the cannons at home.