Engine management was not nearly as finicky as you think. The guys who flew these things were mostly 18 to 24 year olds who were smart guys, but certainly not super humans. The Spit V pilot who ran WEP for 30 minutes didn't burn his engine out. The P-38 pilot whoswho said no WWII fighter had enough power and in combat he just put the engines to full and left them there didn't burn up his engines and Saburo Sakai didn't burn out his Zero's engine running full power in his fight against those fifteen Hellcats.
If I recall correctly, Air fuel ratio, and Spark timing were Adjustable by the pilot. The Spark setting for max power would vary with Boost pressure, inlet air temprature, Air fuel ratio, and coolant temp. All of those factors vary with altidude. Most pilots would pick settings that allowed thier plane to run Wide Open Throttle and not detonate, but that was not Max rated power. To get there would require tweeking. The onset of Knock and detonation could be heard by the pilot and corrections could be make. I would agree that A:F was probably adjusted more at startup and for saving gas on long trips. But Spark timing is not something you could just set and forget, if you want to run Max power at different boost levels.
I've often wondered if when you see dog fights of bud Andersen roping a 109 in a Pony B that were close to equal E-state prior to the rope attempt, whether things like engine management came into play. Perhaps he was cooler under fire and set his engine up during the manuever for max performance, where the German, gambled that his current setting would be enough, and that taking his eye off the target was a greater risk than trying to squeak out a another 50 HP was. Or perhaps Andersen got lucky and he was in the sweet spot for his pony where as the German wasn't.
It could be something that would add realism, and new demention to the game just the way flaps do. Proper use of flaps and throttle will make your plane turn better, depending on the speed, and an ace pilot will learn to optimize those setting to get max performance out of his aircraft. A little engine management would do that also. For example many of the planes had controls to enable/control the superchargers. Imagine if you had to watch and throw the lever to get your second stage to engage at the proper alt in your T-Bolt, or Spitfire.
I think if the performance optimization actions could be added in a way like flap operation, I would be for it.
