I too would hit the fighters early on with the stripped-down Hohen flights. Then hit the fighters again. And again,,,throw the escort timetables off so the Sturm guys can get at the bombers. Bf109G6/ASM spring of 1944 IIRC.....need lots of them before Big Week. Progressively more Mustangs, pilots growing skills and experience vs progressively fewer good German pilots and with replacements, fewer well-trained fliers.
Why were the twin 13mm guns not discarded for wing-mounted 20mm guns? 3x 20mm seems better to me then redesign the cowl and canopy
Because the weight in the wings from the 20mm-cannon and ammunition made handling very horrible. Unless you go for the old MG-FF of course with its very limited ammunition supply. Which actually might've been a good idea (1x MG151-20 + 2x MG-FF).
I think this topic was discussed back and forth quite a lot and the essence is: You can introduce some of the refinements, that eventually anyways, earlier. But other than that, you can't do much that doesn't essentially constitute a new aircraft.
So for me any successor to the Bf 109 F-4 (the best 109 there ever was imo) should have:
- DB605A, with a sound plan to get take-off and emergency power cleared within 4-6 months after introduction
- ADI injection as standard
- 13mm MG131 cowl guns with improved fairing (à la G-6AS/G-10/K-4)
- wheel covers and fully retractable tail wheel
- Erla canopy
- possibly flettner tabs on ailerons
A fighter like this should be capable of 660-680 km/h (guessing), good enough for 1943.
The successor to that would have DB605AS / D engine with otherwise similar configuration. Should be good for 680-700 km/h (again just guessing), acceptable for 1944.
Then the Me 109 lineage ends. The two types above would clearly be transition fighters to hold the line while the more modern and easier upgradeable Fw 190 replaces them as the backbone.