Very creative idea.....You could have entered something like this into the 2008 IL2 Movie Competition. It meets all the requirements (would have to be minimum 3:00 in duration, though)... You are correct, you don't necessarily have to have any aircraft in an "IL2 movie"!!!

As for a story, think along the lines of TWO pilots driving thru the town enroute to an airfield...at an early dawn time/setting. The same exciting music is playing on the radio. The two take off in their two aircraft, going to battle. You don't need to show any air combat at all... Then, cut to a Dusk or evening setting as you show just ONE vehicle returning from the field, driving thru the town... The music is different, very melancholic, solemn... The "message" is clear...
FIN

Wow
 

That is a great idea. Maybe show a history of old photographs of the two growing up together - joining the service together and so on.