Got to say T.A. that sounds somewhat like a new vehicle to me as well, I'd imagine the WaPruf. would see it as such too. Every extension of the length, width & weight of a given vehicle seems to create enormous headaches in transmission strains, engine power, steering difficulty etc. out of all proportion to what seem like minor modifications, & that sounds like a lot of mods.
As for Pz.IV continuing and others being discarded I often think "yeah, why not?" as, in the west at least, even though the last ausfs of mk. IV were really stressed to their limits they still mostly proved perfectly adequate against what was fielded against them.
There's a problem though as it would have required some hindsight for the Germans not to have made Panther & Tiger etc.
The increasingly defensive nature of the fight obviously made the behemoths attractive and it would also be reasonable to assume that the Germans would expect more and faster technological advances in armour from their opponents. The Western allies didn't confront them with as much (vehicular) change as they might have expected but the Soviets certainly did. Without a crystal ball just sticking with the IV could look very much like stagnation, evolve or die.
Then there's the old & valid story of Germany simply not being able to indulge in the massive production that so assisted the allies,
forcing them into hunting technological solutions and heftier tanks. While scarce raw materials and important production time might have been saved by concentrating on the one beast, comparatively little actual production capacity would be freed up. The whole story of initial Panther production seems to be one of
persuading different factories to switch over, and without new facilities (some of which were built) each manufacturer could still only accomodate roughly the same number of under construction vehicles at a time.
I don't think Pz.IV only would have made too much difference, dumping the mk III slightly earlier and going wholly for the IV makes some sense to me... though the thought of solely StuG. production, which really could be churned out quicker makes me go 'hmmm'...
Cheers,
Adam.
(By the way Rodoss, the King Tiger can't really be described as a 'beefed up Panther'... the evolution is far more complex than that & in many ways the Panther is a hugely more evolved/advanced branch of the tree than the Tiger or TigerII ever were
)
...
....
Forgive this long ramble, Just finished reading Spielbergers 'Panther & Variants', so much head-scratching is going on for me over the vehicle
.