wuzak
Captain
Like most new aircraft designs, Mosquito prototypes had significant problems which required at least a year to fix. Meanwhile A-20s were already in production and in combat (with the French Air Force). So I cannot imagine the Mosquito being produced ILO the A-20.
Did they? The second prototype, W4051, went into active service as a PR aircraft. W4051's fuselage was used to replace W4050's damaged fuselage. W4051 subsequently used a production fuselage, and first flew in June 1941, 7 months after the prototype first flew. W4051 flew operationally in September 1941.
The bomber version flew operationally in May 1942 - the delay probably because the first batch of Mosquitoes ordered were PRIs.