p.s. We're building one in Britain!
Ooo, People's Mosquito person! Welcome! The more Mossies in flight the better, in my opinion. They are also building one in New Zealand!
How would you describe the bonded plywood fuselages used by Albatros, Pfalz and Roland used during WW1?
Was the Mosquito a whole new concept or a refinement of an older technology?
The latter, but to be pedantic, with regards to the Mosquito we're not talking specifically about being the first wooden structured aeroplane, but innovative use of that technology at the time, the early 40s. Those Great War designs were indeed laminated wood structures, and yes, they did set a precedent, but remember they were a part of an established norm; add LVG C VI to that list too, and wood construction was prevalent at the time. In the Mosquito, wood construction was, as these aeroplanes virtually the entire structure, which was unusual for a front line service aeroplane in 1941/1942 when it entered service and the reason behind the use of wood also set it apart from its contemporaries, not to mention that it was very good at damn near everything it did, although that's not specifically an innovation.
The first real multi-role combat aircraft
I'd argue B.E.2c and 1 1/2 Strutter beat the Mossie to that accolade, but I get where you are going with that.
I'd offer the Messerschmitt Bf 108 and '109 as being very innovative. Although the Bf 109 was not the first all metal monoplane fighter, nor was it the first to feature the equipment I am about to list, it was the first to combine them in one airframe (although not all at once) and thus it did set a precedent - yes, I know what I just wrote, but bearing in mind with regards to the Bf 108 and '109, setting a precedent resulted from the incorporation of these innovations.
These include a true semi-monocoque structure, retractable undercarriage, landing flaps, enclosed canopy, variable incidence trimmable tailplane, variable pitch propeller, cannon armament, leading edge slats - unusual in a fighter. The Bf 108 also incorporated such modernities as enclosed accommodation, the trimmable tailplane, leading edge slats, variable pitch prop, retractable undercarriage landing flaps all in a semi monocoque structure, not bad for an early '30s light aeroplane. Both designs shared these innovations and did set a bechmark.