ERF:
A very sound theory with the potential to engineer some outstanding vehicles.
Just one problem - who would’ve bought them?
Which marque would apply to which range?
We found this first hand in the late 70’s and into the 80’s. When Guy disappeared, their loyal customers felt so betrayed by BL that they went European or shopping at Sandbach, thus reducing BL group sales. When AEC went, their customers felt the same, not many transferred over to Leyland, who they saw as the enemy. The same with Scammell.
The BL car group tried a development strategy similar to that you suggest with the Rover SD1 car, and came up against the same attitude from the British buyer. Triumph customers didn’t want the Rover body and V8 engine. Rover customers felt short changed by the Triumph designed 6 pot engine and ‘step backwards’ from their advanced P6 suspension.
My personal opinion (and that’s all it is!) sways towards the BL umbrella itself being the problem. If each manufacturer had maintained their engineering independence, and the grouping as we know it had never happened, I think the end products of each marque would have benefited from better and less blinkered engineering development, hindered less by accountant led boardroom meddling. Sure, by the end of the 80’s we would still have lost the weaker marques to history, but I think the rest would have been around for a lot longer - including AEC.Yes…and no in my view.
The Ergomatic cab was a massive step forward for the driver in 1964. Climb out of…say a 1964 ERF KV or Atkinson cab and step into an Ergomatic, and the difference is akin to climbing off a farm tractor and stepping into a car. It’s a lot easier on the human body than any British lorry cab that came before, but as you say, it did lead to compromise. I don’t personally subscribe to the opinion that the Ergomatic cab led significantly to the failure of the AEC V8 though. With adequate time and resources AEC engineers could have completely cured the engine’s mechanical shortcomings, and developed clever and imaginative solutions to the cooling capacity issues, all without touching the cab. A taller cab would have certainly made it an easier job for them though, and made more sensible radiator positioning a lot easier!.
Firstly we’ve had the car discussion previously and as a Triumph enthusiast in the day it wasn’t about the badge it was about the product.In that most Triumph buyers wanted ( were expecting ) the replacement for the Triumph 2.5 and Rover P6 to be based on a development of the Triumph saloon using the Rover V8 engine.We ended up with the ugly hatch back live axle SD1 which alienated most Triumph buyers and a good proportion of Rover buyers so that was a win for BMW among others like Ford and GM in the day and the rest was history for Rover and Triumph.Again leaving the question was it conspiracy or ■■■■ up.
As for the cab issue.It’s clear that the Mandator V8 was a schizophrenic mixture of Perkins and DS14 so as to fit the wrong engine in the wrong cab for the vehicle sector it was aimed at.IE the poor bleedin thing didn’t know what it was and was effectively no good for anything because it wasn’t one thing or another and made as much sense as Scania chopping down the DS14 in order to make it fit under 81 series cab.I can just imagine the Swedes saying why the zb are we doing this and what is it actually for and we’re going to end up with the worst of all worlds of a big engine with all the downsides of a small one doing a big engine job and a small cab that also needs to be a big one.The thing really was nuts. 
