a possible house rule, if someone knows the historical practice:
Limit how far you will extend your armored spearheads, beyond supporting infantry.
My question is, for instance in the historical Barbarossa, was there a specific German doctrine about this? Did Guderian, for instance, limit his advances by any consideration for how far his radio range was, how far a tanker could transport fuel, or how far back the infantry was? Or did he and other commanders just go hell for leather? If they did limit their advances, what is a good approximation in terms of hexes in the game?
Well, I don't know if there was a specific limit in their operational doctrine ... except, perhaps, "as far as you can" ... but there were practical limits ... the number of trucks available to run supplies, mainly POL, from wherever the supplyheads were to wherever the Panzers were in fact.
There's a whole excellent chapter in Van Creveld's "Supplying War", which should be available on Amazon or through interlibrary loan.
Basically, the Germans had such limited resources at all levels they couldn't produce enough trucks to supply the sort of mobile war they would have no doubt liked to fight ... throughout the war the Wehrmacht never had more than 15% of its total forces that were motorised (including Motorised, Light, Panzer and Panzergrenadier) by actual combat and logistic unit strength (at the end of the war, all the understrength "shadow" divisions raised by Hitler's whim, almost, don't actually change this ... look at the actual strength they fielded rather than the nominal TO&E strength for confirmation).
As a comparison, the British Army was 100% motorised from about 1937, and the US wasn't far behind. The Russians were much like the Germans, about 15% of their forces were actually motorised.
The problem the Germans faced when invading Russia was so severe that they had progressively scavenged trucks from all their conquests to date to scrape up something vaguely resembling "enough" (if you didn't look at the problem too closely, that is) ... so you had several score, over 100 IIRC, different models ... Polish, French, Belgian, Danish, Dutch , British (captured from the BEF), Czech, Yugoslav, Greek ... anywhere they'd holidayed ... being used, which, in and of itself, was a nightmare, logistically.
Then there's the issue that the standard German truck design evidently wasn't all that robust, especially for conditions on the Eastern front, and wore out quicker than US/British/Russian trucks.
All in all, it was a cobbled together shoestring operation that had to win quickly before it all started to fall to pieces.
The idea of "blitzkrieg" was short sharp campaigns, over quickly ... and simply fell apart when thet wasn't possible.
Even the western allies had problems with supplying continual motorised operations (read up on the Red Ball Express ... to keep it running they basically had to strip all the trucks from several divisions that were, consequently, left immobile, to keep the supplies rolling forward).
There's a lot more, like the shortage of POL tankers on the Reichsbahn for starters, but it all boils down to the fact that the Germans were operating on a shoestring ... they could have built more trucks and/or tankers, except that they'd have had to build less tanks, planes and the like ... they were operating that close to the bone the entire war.