Well, 'some loopy SS standard of Aryan' is rather easy to do, given that they made the Japanese 'Honorary Aryans' and considered nearly everyone else in Asia trash.
For example, maybe they begin sorting through West Slavs to find those with suffucient 'Varangian' ancestry to be tolerable by the Germans.
I think people are underestimating the Reich. The reason they built up such a large military-industrial complex was to fight the war that everyone knew was coming. At the end of a WW2 victorious for Germany, it would be spent. There would be no war left to do, besides the partisan struggle in the USSR. I think even Hitler might eventually realise that one shouldn't keep building weapons forever if there is no war left to fight.
Besides, even if Germans are not happy under Nazi rule and revolt in the sixties or seventies, the German state would not collapse. The Weimar constitution still existed, in theory Germany still was a parliamentary democracy. The Wehrmacht would likely side with the people, so that leaves the SS, who are far more fanatical but far fewer in number.
Of course, I might be completely wrong. What are your views?