Flame-Prop,
I'm not sure there could be any more clickables within the cockpit of the Warbirdsim Mustangs than there already is, at least when it comes to everything used to start the aircraft. There is already a ton of my own written code, just so that there is far more functionality within the cockpit than what default-FSX/Acceleration coding supplies. Unfortunately, and I am being very serious about this, I would need a college degree in C++ and probably something more, to do really anything more than I have with these products, and have the features I know you're describing. The capability to provide that final measure, as you describe, is something that only a very, very select few individuals have the learned knowledge/invested schooling to do.
I like to think of it this way - even if you have to have a slightest bit of imagination, you can still run through the start-up procedure, using the exact same switches/levers as in the real aircraft, as they are all included, and all function. I probably shouldn't be as proud about it as I am, but both "Little Friends I" and "Little Friends II" even feature a very functional automatic supercharger (something that default FSX does not provide support for), that does at altitude exactly what you would experience in the real aircraft. At around 17,500 ft, you will definitely notice when the supercharger switches from low blower to high blower, just as you will notice when low blower, and then high blower, begins to run out of steam the higher you go (which, accurately, isn't quite so noticeable with low blower, until you reach about 8,000-10,000 ft, when the available power begins to start to die off a bit as you continue higher, until high blower automatically switches on (just as it does on the real aircraft, automatically) and you have enough power to just get you to the P-51D's max service ceiling of roughly 40,000 ft - which could just be reached, on a good).
I'm very glad to hear that you are enjoying the aircraft! I hope that it can be understood that I try to provide as much as I believe I feasibly can, with the knowledge and available resources I have at my disposal. Where in aspects I can't produce in, I try to compensate for with everything else you see and experience.
-John