Well. ya know seriously here...we now have a P-47M that was produced in very low numbers (130)...even though we have vastly incomplete plane sets for other factions. Modifying the loadouts available to the existing Stuka models would be a very minor infraction on the "historical accuracy" issue.
That we now have the P-47M or how many combat hours a plane has is irrelevant to this discussion.
Spit16's had 23 TOTAL hours of combat time.....they weren't seen flying around in droves like you see them here. A spit16 never scored a single kill in WWII, so if we're going to split hairs on historical accuracy, let's get serious.
The Spitfire Mk XVI had more combat time than that, not sure of the exact number of hours but it was far more than 23. You are also incorrect about not having any kills. TB 752 flown by Flying Officer ‘Bob’ Young shot down a Fw 190 and a couple of days later, TB 752 agaub scored another A2A victory when Flying Officer ‘Fred’ Town shot down a He 111 (TB 752's "Final Victory" is depicted in the painting by Michael Turner). You can read more about TB 752 and the pilots that flew her in combat in the book, 'The Manston Spitfire - TB 752'.
So, now let's get serious...
You are wishing for something that never existed on the D-3. Since you're so willing to chuck historical accuracy out the window, why not ask for lasers or an AMRAAM missile system?
The simple fact is that the D-3 never carried 20 mm cannons on the wings, the wing design of the D-3 couldn't fit 20 mm cannons.
ack-ack