Innominate, what you say would be true for a steady state peacetime force, for example the Typhoon force requires half the number of aircrew compared to the Tornado force (simplistically).
Now assume 1500 Mosquitoes and 500 heavies or 500 Mosquitoes and 1000 heavies.
Now assume monthly attrition of 5% and 10% respectively.
In the first case you would lose 125 pilots. In the second you would lose the same.
Now consider engines. First would lose 350 engines compared with 450 in the latter.
Clearly in this simple scenario the Light bomber force is much more economical in aircrew and engine attrition and neutral for pilots. I would submit though that it would not have been an impossible force structure.