There are a number of assumptions underlying your argument that, if examined, challenge the notion that a continental superpower would have been unbeatable even with time for Britain and France to arm or rearm.
1) Germany defeats the Soviets quickly and painlessly: If Germany fights a protracted war with the Soviets and sustains even half its historical casualties on the Eastern Front, that's manpower and material not available for later. Keep in mind, it might only take Britain 2-4 years to rearm to the point where she feels confident that she can dictate terms to Germany, assuming France has also done the same. If Germany initiates a war with the Soviets (or gets attacked by the Soviets) in 1939, and doesn't win by 1941 while Britain continues to rearm, the balance of power does not swing Germany's way for some time.
Note that occupying a significant portion of the Soviet Union, and actually forcing them to surrender, are not the same things. A historical partisan campaign against Axis occupation would still tie up resources even if the Germans make it to the Urals.
2) Annexing the Soviet Union solves Germany's resource deficits in critical areas: Annexing the Soviet Union may not end up solving Germany's resource deficits. It would help, but if Tooze is right, Germany is still in a deficit for critical things like food. That means Germany has to have a navy, which it can't build up fast enough or large enough to challenge British naval superiority (to the point where Germany can ship resources freely). It would take years. Even the Germans didn't think they could reach 35% of British naval strength before 1943, and that's without fighting a war. It would take years to reach any kind of naval parity with Britain.
3) Germany is just as strong without occupying France and Benelux as she was historically: If Germany only marches east, France remains intact and Germany cannot occupy or extort resources from metropolitan France, nevermind Benelux. Let's not forget that the "continental superpower" that you claim "it took half the world to defeat" managed to seize the industrial heartland and coal reserves of France, a major power in its own right. Also, a rearmed Britain would have far more than 13 divisions to contribute to the defense of France the longer they have to rearm. Sure, you can ridicule the French army all you want for failing to defend France (I won't, but some folks do), but adding another 1,000,000 British troops to the defense of France would make a significant difference; the mere presence of a place for those troops to go and defend in the first place would put Germany in a difficult position even if the French army doesn't further modernize or improve its manpower position.
4) The German people don't care about consumer goods or the economy: A further consideration is civilian demand for consumer goods. If Tooze (and Schacht for that matter) is right again, further German rearmament would have resulted in economic failure. So Germany either has to slow down further militarization, loot resources from the Czechs, French, Dutch, and Belgians, or mobilize fully to war footing and hope the people accept it. I wonder if the German people would have been nearly as accepting of a large war with a lower standard of living and no quick victory over France to buoy Nazi political support.
5) Germany has the freedom to commit 100% of its military strength against the Soviets: Just because the Nazis and Soviets spark a huge war in Eastern Europe, it doesn't mean that Germany has no military commitments in the west. In fact, the irony is that if Germany does commit everything to a war in the east, France and Britain have an easier time demanding stuff from Germany. If Germany doesn't commit everything to the east so it can cover its western frontier, then it's back to the problem of 1941, where even though there is no fighting in France, Germany has to station forces there to cover the area in case of attack.
The irony of this discussion is that it reveals how useful the M-R Pact was. Whether Germany attacked France or the Soviets first, without a clear guarantee that they wouldn't be attacked from the other direction, Germany's position was precarious. If Britain and France just use the time to rearm while Germany and the Soviets fight each other, they could be in a far better position than they were historically, even if the Germans manage to somehow win.
And while you think the M-R Pact didn't work, I would argue that it helped the Soviets immensely. The catch is that the Five Year Plan in effect during the M-R Pact assumed war in 1943, so they weren't done rearming. The pact wasn't a problem; Germany breaking it ahead of the Soviet timetable certainly was.
EDIT @stayfroty: And as for the French army being the largest in 1939, it was certainly large. However, many divisions in 1939 were reserve formations with crappy equipment and older soldiers. These reserve formations were also not trained very well. You can't fix the age of soldiers, but you can fix the equipment and training problems with time and material.
