1.) I think that everyone is overestimating the accuracy of strategic high altitude bombing. The USAAF post war strategic bombing survey showed that accuracy during the war was vastly over rated.
2.) I think the effectiveness of German AAA is vastly underrated, again according to the USAAF statistics half the heavy bomber losses were due to AAA. With radar guided proximity fuse's this danger wouldn't have diminished for the mosquito.
4.) The number of Mosquitoes would have been double what was required for the heavy bombers. This isn't due to bomb load, this is due to manufacturing demand for spare parts and airframes to keep the number flying correct. So lets assume a 1.5 multiplier to carry the equivalent bomb-load as the heavy bombers with an additional multiplier for spares and repair parts.
1. I totally agree, no matter what plane was used, the actual effect on the war would not have changed. The effect on casualties and costs on the other hand...
2. Smaller plane is less likely to be hit by AAA and generally it is harder to hit a faster moving target, but much more important - the time spent in AAA is significantly lowered. AAA avoidance is a big argument favoring the mosquito in daytime.
4. The major complexity and cost in maintnance comes from the engines. So roughly one 4-engine bomber is roughly similar to a pair of 2-engine bomber. The total number of crew in a mosquito is less than half that of a B17. The cost in fuel per lb. explosive delivered is better. In all efficiency parameters the mosquito was superior by a large margin. The whole development of the mossie and the idea to remove all defensive armament was driven by pure efficiency calculations (extensively described in Sharp & Bowyer).
i know you're about to try to say that the interceptors would never catch the mossies.......but you would be very wrong.
all that would have been required for them to catch them, would be to be at altitude before the buffs get to their interception point(as they often were anyway). then it would be a matter of diving on them, take the shot, rinse, and repeat. this would have been devastating to the mossies, as the bomber version was(i think) undefended?
Catching the mosquitoes with fighter marginally faster requires a very careful setup and accurate guidance to intercept. Any interference (escorts and forward fighter sweeps) would ruin any carefully prepared defense. By not relying on massive boxes for defense, the mosquito raids can be in several waves not letting the defenders time to refuel and reorganize after the previous wave - especially if their total numbers were higher than the B17 (~twice?) it would overwhelm the defenders. As someone mentioned above, destroying one mosquito allows the other to reach the target - half a B17 is not going anywhere. In any environment that involves clouds, a single mosquito has a far better chance to escape enemy fighters than a single B17 with all its useless guns, by diving into the clouds.
Finally, for casualty calculations, in terms of crew, a loss of a B17 equals five mosquitoes.
I guess that the real reason mosquitoes (or similar) were not used by the 8th is that A) American industry was not as adept as the British one in woodworks, but the could be overcome. B) Would the US fight its war with a non American main bomber. Can anyone even imagine that? and C) Not enough people believed it would work just because it was a new and radical concept. Remember that even for the RAF it took a lot of time to digest what De-Havilland was trying to sell them.