Jetex Jim. Also remember that one of the points of the Mossie was to make use of a cabinet making industry that was, otherwise, making little contribution to the war effort. That industry was finite, though, and was probably working close to its capacity. Additionally, all that balsa wood to sandwich with ply had to run the U-Boot gauntlet from South America and was in competition with other essential war material.
Now, a metal Mosquito would have been interesting and would probably have better utilised skilled airframe (metal) fitters and myriad semi-skilled workers than churning out Stirlings and Halifaxes.