Chugalug,
The problem is that for most of the War, the night bombers went out, night after night, and failed to hit their targets, and indeed to inflict damage and/or casualties that came anywhere close to outweighing losses. Occasionally, and more often from 1944 on, they caused massive civilian casualties and disrupted industrial production.
Did German bombing cause a collapse of UK civilian morale? No. Do you think allied bombing did anything different?
Did Allied bombing actually force dispersal and more efficient production methods?
Weighed against that I can't see how medium bombers could have done any worse, and they would most likely have done much better. Bear in mind that every Lancaster and its seven aircrew could have been two Mosquitos. How many targets could the Mosquito not reach? How many more targets could a Mosquito have accurately bombed than a single Lancaster? How many Mosquitos and crews would have survived? And that's if you just chose to hit the same target sets.
They could have been making life impossible for German forces in France and the other occupied countries. They could have made it impossible to complete coastal defences, and could have disrupted the supply of ammunition, supplies and food to the German defenders. D-Day might have been a lot easier. They could have remorselessly hit the German airfields and V-weapon launch sites.