How did the Nazis plan to avoid severe inbreeding?

[dead0man]

What's the problem? Even under the narrowest definitions, there were tens of millions of Aryans at the time. They could easily have only married each other without genetic deformities.

that's my thinking too.  I don't know how small a population can be without risk of inbreeding, but I know it's a WAY smaller number than whatever the Axis would have ended up with if everything had turned out perfectly for them (even if you leave the Japanese out of it).