You write:
- (afaik the 1924 Mercedes functionality was later emulated by Alfa Romeo in their Tipo B/'P3' and 'Bimotore' cars)
http://www.grandprixhistory.org/alfa-romeo-bimotore.htm
Quote from https://www.forza-mag.com/issues/154/ar ... ity-clause
Alfa Romeo Bimotore 1935

Some more details:

All this "complexity" was necessary in order to utilize two long engines: an in-line 8-cylinder engine in front of the driver and another in-line 8-cylinder engine behind the driver, with a common gearbox / differential at the middle of the car (the drive wheels were the rear wheels).
I can't see how this architecture affects the inertia torque on the engine casing.
You also write:
- the point of the Mercedes axle is that each wheel/road contact load is unaffected by the engine power being used
Sorry but, again, I can’t get how the Mercedes axle eliminates the inertia torque on the engine casing and on the frame of the car.
A drawing / plot / photo would help.
Thanks
Manolis Pattakos