Is the RAF any worse off if they have just the Spitfire, Mosquito and Lancaster?
For this to work in time to cover all all RAF ops from Sept 1939 onwards, we need the Avro Manchester to go four engine right from its onset and the Mosquito to get more Ministry support. Neither is ASB, especially if these three aircraft are to form the RAF's strike and fighter force.
Of course I've chosen the three best aircraft that could be available 1939-1945, so yes there is an element of ASB here. However, if we give the RAF just these three combat aircraft, can they still do as well or better than OTL? Some losses, such as the Sunderland and Beaufighter will be hard felt, the Blenheim and Hurricane less so.