A good and realistic compromise would be to go by what was standard operating procedure, as this was usually decided by the test crews who would stress the engine to its limits so that the pilot wouldn't have nasty surprises in battle.
For example, i've flown the Spitfire add-on for MS FSX in a friend's PC. We have spitfires running around with throttles wide open in IL2, but in reality the maximum continuous boost allowed was +8lbs. You could exceed that but you had to keep an eye on the temperature gauges and then let it cool down, which adds another very important dimension to air combat...making sure your motor is cool before the fight so you can abuse it for a couple of minutes. This would also end the unrealistic continuous furballing, because people would have to disengage to cool their engines every now and then.
Another thing is that just because the throttle lever has a certain amount of travel, you don't need to jam it wide open to take off. Manifold pressure is a function of external air pressure, you need less throttle to achieve a certain power setting at low altitude than you would need when you go up at altitude. For example, in the Spitfire add on i talked about you only needed to move the throttle about 60-70% of the way in to achieve take off power, maybe even less, because there's enough outside air pressure to give you the manifold pressure you need.
This would also have a very good side effect of balancing the sides in a realistic manner. The allies had better performing or easier to control aircraft, but most of them had manual engine systems. The axis on the other hand had aircraft that might be less maneuverable than a spitfire and slower than a P47 at altitude, but the pilots usually didn't have to touch anything apart from the throttle.
What we have now in IL2 is exactly the opposite of what happened in reality, FW190 pilots using manual pitch to get what was the historical performance of their rides on automatic settings, while P47s cruise around on WEP and 100% pitch while in reality they had to monitor manifold pressure, RPM, intercoolers, radiators and turbo-supercharger speeds. I'm not complaining for what is an inherent disadvantage of a 10 year old engine that never the less scaled really well to more modern PCs along the years, but i would like to see it changed in BoB:SoW. It would be cool to fly by the engine instruments instead of the % pop up messages that appear when moving the throttle
