I definitely like the idea of adding more immersive elements to a flight sim. However, I believe that the focus should always remain on the flying.
What a sim like SF2 would benefit from is:
1) Context
The campaign introductions are great, but after that there isn't a great deal of background info. Along with each mission briefing there should be some general "campaign" information, possibly in the form of news headlines, that indicate the progress of the war. The historical campaigns could even be fleshed out with details of important military or political events happening at the date of that mission.
2) Greater sense of cause and effect
I don't mind flying 20 strike missions to bomb a warehouse or repeatedly bombing runways, but I'd like the game to tell me that my outstanding success has had an effect on the war. I'd like to know that, for example, the bombing of that warehouse has led to the enemy tank battalion being unable to progress to their objective, or has decreased their combat effiency. I'd like to know that my SEAD sortie has led to the success of the other flights in the region, or that attacking the runway will disable that airport for the next 3 weeks, or something to that effect
3) Pilot progression
I see where you are going with the RPG elements, but I don't think that they should directly affect our flying ability. I like the way the old Red Baron game handled it. As you increased in rank and prestige, you get more influence in choosing your personal aircraft, airbase, flight arrangement etc.
At present, in SF2, whether you are an Ensign or Captain makes no difference. Also, its odd that my rank and kills from flying in the Suez Canal crisis gets automatically carried over to a career with the US navy. Different campaigns should have different profiles similar to the IL2 sturmovik series.