Since there are plenty of historical cases of P51's being misidentified as 109's why not throw a randomizer on the ID and make it wrong sometimes! now we're talking about some serious reality and fun.... And more to the point, historically, missing a P51 as a 109 means that you also ID'd a friendly as an enemy... Yeah baby, BRING IT.
Just give Grey tags of 'Bogey' to planes beyond 1k... Then as you get closer you get a chance of successful ID based on the number of known friendly eyes nearby and dependent on your proximity to friendly radar! Yeah, now we're getting ridiculous.. lets keep running...
In 'Duel of Eagles' there is one story of a 109 joining a flight of Hurricanes of 85 squadron... 85 had no idea it was a 109 until it started lighting guys up... Yeah, now thats good gaming.
Bring it, you've been served!