As for what they could have known, as someone (I think Admiral Beez?) noted already just upthread a little, all they had to do is look at what the Japanese and US were doing and realize that a two seat fighter wasn't a great idea. Maybe they didn't see that clearly in 1938, but certainly by the time the Firefly was being designed it should have been clear.
No internet in 1938-39
In 1939 the US was fooling around with 12 F2A-1s starting in June. In Aug 1939 the British Purchasing commission is looking an export model of the F2A-2 and final comes up with the cash in Jan 1940.
It took until Dec of 1939 for Brewster to deliver 11 of the F2A-1s and put 9 of them aboard the Saratoga to operate with F3F-1s
So maybe looking at what the US was doing, unless invited to go behind scenes may not give the best results?
Looking at what the Japanese were doing could be hazardous to one's health. Again timing is everything. Getting an intelligence report from China in 1940 when you already have the Fulmar in production and it is going to take several years to replace it with a totally new plane doesn't do the British a whole lot of good.
I've been arguing, throughout this thread, in post after post, that they didn't need to wait for a 2,000 hp engine and that waiting for one or planning an aircraft around it was one of the key mistakes they actually made.
Ok, in 1939 what are your options for a British engine?
The Vulture, Sabre and Centaurus are off the table.
The Hercules is also getting real fuzzy looking. Bristol is having production problems and Bristol and Vickers are looking at using Merlins to make up for expected Hercules production shortages, in fact Vickers is looking at buying P&W R-1830s for the Wellington and Bristol is looking at buying R-1830s for the Beaufort.
In 1939-40 you are looking at some form of Merlin ( or a 9 cylinder Pegasus).
Now what kind of plane are you going to make in 1940-early 41 starting in 1938-39 with the versions of Merlin that you KNOW will be available in 1940-41? You may know or expect certain models of Merlins to show up a number of months before they actually arrive maybe even a year. What you don't know is what the actual boost limits will be as the fuel is changing through late 1939 through 1941.
Now the British critics blow off the homing beacon operator in the back seat because the US didn't need one. The question here is didn't need one when? and what were the US fliers doing to compensate? Using the SBDs or TPDs as navigators? Also radar was just coming into use, Sometimes a carrier could give radio direction to lost fighter, sometimes not.
The US used SBDs or their predecessors as scout aircraft, the whole Scout Bomber thing as you know.
The radio gear (lumping the homing beacon in here) changed during the war, sometimes more than once.
British carriers had shorter flight decks, They had less hanger space and they also had way less fuel. They could not put up short duration patrols and change aircraft at frequent intervals even if there was no (or especially if there was no) contact. The British needed to find things that worked for them, not copy what worked for the US.
Sometimes what worked for the US could be used, sometimes not.
The British did screw up a lot of things. But so did the US.