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I'm surprised they didn't at least try something like the Malcolm hood. It would have required no redesign of the aircraft itself, probably could have been fitted to aircraft in the field after production.
Maybe Willy Messerschmitt was more interested in selling his new designs (Me209, 309) to the RLM, instead of improving his old products to where the new ones wouldn't be needed.
A true bubble canopy would have required major redesign of the fuselage, but just a Malcolm hood design, like the Avia, could have been done with no redesign of the fuselage.
And much better than the Erla version.