It might be helpful to approach this by defining the maximum possible shapes of German victory and seeing what those victories buy them. I think you'll see that even the maximum German victory in the east leaves the Germans far weaker than most people assume.
Before I go on, I want to emphasize that I'm not at this point interested in how feasible these German victories were. I'm just interested in the aftermath of those victories if by some combination of German luck and Soviet errors the Germans won them.
Maximum possible German victory: The Germans were not going to occupy all or even most of the Soviet Union. The best even marginally possible German victory could come in one of three forms:
(1) The Germans take enough of the economically important parts of the Soviet Union to take the Soviet Union out of the Great Power category, leaving them as sort of a Nationalist China analog written large--still fighting but only tying up a manageable percentage of German power. That would probably require most of the following (a) Making the rail nexus around Moscow unavailable to the Soviets, (b) Strangling Leningrad to the extent that it was no longer producing significant military power (manpower and weapons) (c) Taking enough of the good Soviet farmland to keep the Soviets from feeding themselves (d) Denying Soviets access to the Caucasus oil (e) Limiting the amount of manufacturing capability that the Soviets are able to move to safety.
(2) The Soviets accept some sort of separate peace that gives the Germans the most important parts of what they want.
(3) The Soviet regime disintegrates, like the Tsarist one did, leaving a power vacuum.
Before you jump in to argue that none of those are likely or possible, let me emphasize again that I don't really care about feasibility for the moment. I'm just trying to explore the consequences if the Germans got as much of what they wanted in the east as they could have under the most favorable circumstances.
Under any of those victory conditions, the Germans have a continued bleeding wound in the east. The whole point of heading east was to exploit Slavs as part of a process that eventually enslaved them or replaced them with Germans or related 'racially acceptable' people. Under those conditions, partisan warfare in the conquered territories was a given. The size of those territories, the scarcity of roads and the good guerrilla terrain--swamps and forests would mean that winning that partisan war would be long and difficult as long as somebody from outside was supplying a significant amount of weapons. Even if the Soviet Union collapsed or made peace, significant arms production capability would still exist outside German control. The Soviets would almost certainly not halt shipments to partisans in the long term, though they might reduce it in the short term as part of a peace treaty.
The more of the Soviet Union the Germans took, the larger the number of occupation troops they would need. If any significant part of the Soviet Union remained outside German hands, the Germans would have to station significant numbers of troops along the border between the conquered and unconquered areas. Even if the border was lightly guarded in any one spot, the sheer length of it would require a large number of troops. The western Allies would not face anything close to the full might of the German army, even under the most favorable conditions in the east.
While the parts of the Soviet Union the Germans could feasibly conquer have a lot of natural resources, the infrastructure to exploit those resources would take years and enormous resources to build, especially given Soviet scorched earth policies, partisans and German policies that at least initially were impractical. We're talking an enormous investment in roads, railroads, farm equipment, etc.
If the Germans were still fighting the Western Allies, they would have to choose to some extent between war production and building infrastructure in the east. Granted, they would be able to exploit the manpower from conquered territories to do some of the building, but even that would take away from war production that slave labor would otherwise be used for.
Figure the Germans would be somewhat stronger than they were historically by 1943-44 given maximum feasible victory in the east, but by no means would they be the colossus that the Allies feared would result if the Soviets collapsed. The war might last several months to a year or two longer, depending on how many A-bombs the Germans were willing to eat, but ultimately the Germans would lose.
At that point, the western Allies would inherit all of the disputes in Central and Eastern Europe that the Soviets brutally settled after World War II historically. German nationalists in Danzig? Settled. They either fled, died or decided they weren't really Germans. German nationalists in Sudetenland? Settled. For the most part they aren't there anymore. Polish/Ukrainian fighting in the borderlands? Settled. Not many Poles left to fight there. Stalin put Poland on wheels and moved it west a few hundred miles.
Massive ethnic cleansing, yes. Brutal, unfair, bloody? Yep. But Stalin permanently settled quarrels that were hundreds of years old. I doubt that the Western Allies would have been able to do that.
