The engineers and draftsmen turned, in 1935-40, quite a few aircraft from napkin sketches into flying hardware. Just monoplane fighters: Vickers Venom, Bristol type 146, MB-2, two Glosters, plus 4 fighters that RAF accepted in service, plus Fulmar = ten designs. With bombers, transports, civil aicraft, hydro/flying boats, and other naval aircraft counted in, that is serious number of aircraft.
What will be a problem is turning the flying prototypes into mass produced aircraft, as you've noted. One of reasons I've mentioned a wooden fighter.
Actually a few of the planes listed illustrate the problem. the Bristol type 146 was
designed to the specification F.5/34 but first flight by prototype wasn't until 11 February 1938 at which time not only was the Hurricane in production but first aircraft had started to be delivered to service squadron/s. The Bristol was behind by at least a year and closer to two years. As for one of the Glosters: from Wiki" By the time the F.5/34 began its flight tests, the 8-gun Hawker Hurricane was in service and the Supermarine Spitfire in production so that further development of the Gloster fighter was abandoned." Granted it goes on to say " However, compared to its contemporaries, test pilots found the F.5/34 prototypes had a shorter takeoff, better initial climb, were more responsive and manoeuvrable due to ailerons that did not become excessively heavy at high speed. Handling was considered very good and the all-round cockpit visibility was far better than the other designs." However you run into the engine problem. Both are powered by the Mercury engine and without major work there was no more power to be had. The
only possibility is using a Perseus engine and even that is only going to get a few more HP until sometime in 1941 even if you can get it to match Hercules power per liter. Of course you have to solve the sleeve valve production problem too. Switching engines to Taurus or American radial means a delay of a number of months in planes that are already running late.
I'll like to return to the foreign countries trying to license produce the Hurricane: all was fine until there are Merlins to be purchased. Problems arose when that was not the case, Yugoslavs went to have DB 601A installed in their Hurris. A more widely spread engine in an airframe better suited for it avoids these problems.
We are back to
which more widely spread engine? the more widely spread engines are down on power (in some cases waaay down) and/or have limited development potential.
Most countries and foreign companies are
only interested in licencing aircraft and engines that fall in a narrow band. It has to be more modern than they can design themselves but it has to have enough of a "track record" to be a somewhat proven design. Very few, if any, Countries/companies licensed experimental aircraft or engines. They wanted value for their money, not to be funding other peoples research.
Some countries were limited as to who would deal with them and others had different ideas of how long they had to rearm.
The problem with Dagger VIII is that it was a lousy replacement for the Pegasus. In a bomber, it needed to go in emergency RPM and boost to beat Pegasus, while being 250 lbs heavier. We don't know how good the cooling was in 250 MPH bomber, vs. a 300 mph fighter. How much the max take off setting was used in a fully laden bomber, vs. a fully laden fighter? All these things can push the engine into overheating, let alone combined.
It doesn't look like that good a fighter engine either, FTH was 8000-8500ft without ram. Power at 14-16,000ft wasn't much better (if as good) as the Mercury.
The tooling for Kerstrels was around for quite a few years, and some of it will not suit Merlin production, but will future Peregrine production.
"Tooling" covers two things. the jigs and fixtures used to hold the parts in the machines, the gauges used to measure them
and the lathes, milling machines, drill presses,etc the jigs and fixtures are mounted on. The Jigs, fixtures and gauges specific to the Kestrel
could be give/sold to someone else but RR is going to need every single lathe, milling machine, drill press and broach they have.
A more emphasis on production of the 2-pich and variable pitch props might come in handy? Buy at Hamilton Standard? License production of those, either in UK or Canada? British were not shy to purchase licenses, from Farman's S/C drives to Bren/Oerlikon/HS/Bofors.
Britain had fooled around with controllable pitch propellers back in the 20s. Henry Selby Hele-Shaw being one of the inventors, however, like many things the
idea was ahead of the ability to manufacture and the biplanes of the time had such a limited speed range that there was considerable argument about wither the benefits outweighed the cost (money, weight, maintenance). Unfortunately the "wisdom" of the time tended to stick and prejudiced the Air Ministry against the variable pitch/constant speed prop for years to come. de Havilland had bought the Hamilton Standard license in 1933 but they were trying to sell to an air ministry that didn't want to buy. Rotol was formed by both Bristol and RR not only as a competitor but as a 2nd source as both Fedden and RR management
knew the better props would be needed soon even if the air ministry had both thumbs firmly inserted in their collective backside.
Under 'they managed' I've meant 'they managed to take off' - despite small wing and take off power. The MC 200 also managed, so did the Bf 109 versions with MF FF and Jumos.
Granted, the Fokker carried half of the armament, but extra 200-250 lbs worth of guns ammo does not sound like a reason for the wing area of 174 sq ft to grow 50%.
By 1941, the 'other' fighter can get the better engine, per 1st post here. So the Japanese (or other) cannot rack scores so easily.
Well, something was going on as the Bristol 146 had a 220sq ft wing for 4600lbs and the Gloster F.5/34 had 230sq ft for 5400lbs. MB 2 had 212 sq ft.
Not all countries had the
same take-off and landing requirements and the British ones
may have been severely impacted by those two bladed fixed pitch props. Some other counties getting on the constant speed (or at least variable pitch) several years before the British Air Ministry.
One of remedies is to use more powerful engines as they became more available.
For the British the only more powerful engines that became available were the Merlin and Hercules, unless they could buy P&W R-1830s or Wright R-1820s. While the Mercury and Pegasus got a bit better with 100 octane fuel it wasn't a lot better and it didn't change the FTH any.