As I may have mentioned before I think Nuffield is a scapegoat for a lot of mistakes made by the War Office and Army.
That is a fair point, certainly he blamed the Air Ministry for keeping changing the specs on the Spitfire that his workforce at Castle Bromwich had to keep adapting to. Likewise with his tanks. He was certainly willing to offer his company's undoubted experience to the war effort. I would argue that the problem was with lack of designers of tanks, rather than simply a company good at making cars trying to transform into a company making tanks.
That's the whole point of the storyline. Yes the Matilda II was a good tank in 1939 and 1940 (armour and gun, not speed nor range) . Yes the Comet and Centurion were very good tanks in 1945 (the Centurion still had range issues). As the inventor of the tank, pre-war the War Office had got itself into a muddle: infantry vs cruiser; speed vs protection; etc.
The Cromwell was a good tank, or would have been in 1941/2, by 1944 not so much. The Crusader's problems, like the Covenantor, wasn't just the engine, but also the cooling system, a design fault. The Churchill was good a climbing hills, but shouldn't have been let loose until it was actually working properly.
Meanwhile the Panzer III and IV were developed and in the case of the PzIV was still useful 'till 1945, and the PzIII as stugs etc. Yes, the big cats had problems, and weren't as numerous. Excluding Light Tanks: The Yanks moved from the Grant to the Sherman to the Pershing. The Soviets moved from the T34/76 to the T34/85 and from the KV1 to the IS1. The Brits had Matilda I & II and A9, A10 and A13; Matilda/Churchill/Valentine and Grant, Covenantor and Crusader; Churchill and Crusader & Cromwell; Churchill, Cromwell and Sherman (inc Firefly); Churchill, Cromwell, Comet and Sherman...
That wasn't Lord Nuffield's fault, that was the war office not having a clear understanding of what tanks were for and what, therefore, tanks needed to be like. I agree that if the War Office had given Nuffield (and LMS and Vauxhall and Vulcan) proper help with design, proper oversight on production quality, and had sorted out the gun issue, then yes, the Crusader, possibly even the Covenantor, might have been good enough. But the didn't that was part of the reason (in part) for the Great Tank Scandal.
What I've written about the A15 comes from OTL, I haven't changed anything. Likewise the A22 (Churchill) except taken the panic out of the process and given the two companies time to properly go from prototype to production.
My keeping Carden alive, meant that instead of Little finishing the design for the A9, A10, A11, and Valentine, Carden completes his drawings. Vickers was basically the only company experienced enough to design and make tanks (though the loss of Carden impacted that badly). The Valentine in TTL is the Valiant. Better protection, room for improvement, better engine. The Victor is somewhere between the Cromwell and Comet and will be available early 1942. So if Yanks go Grant to the Sherman to the Pershing, then the British could go Valiant to Victor to Centurion clone.
Anyway, that's my intent, not to scapegoat Nuffield.
Allan