While I take your point I think that the sheer scale of the problem would cause the headache for Germany. I understand what AH wanted for the lands in the East and the cleansing of the Slavs and other sundry Untermensch.
But that couldn't happen overnight and immediately after the conquest there would be many millions still in these lands. It wouldn't be easy to achieve this cleansing in short order and once the people realised what was on their particular menu then I can't see them lying down and rolling over until it happened. There would have been widespread resistance which would not have beeen easy to control especially if aided from outside.
But also assuming that it was achieved fairly quickly then one is presented with an empty land and a mere handful of millions of German settlers as opposed to the hundreds of millions of inhabitants that occupied them before with plenty of space for them as it was.
One would have a land with extremely sparse human control and a very vulnerable land at that to outside interference and leftover partisans.
Short of driving vast hordes of people eastwards to form a mass of people in rump Russia I can't see how it could be easy for the Germans to achieve an early ethnic cleansing. Plus Germany would just be creating a potential returning army armed by Russia and just possibly the USA. Assuming any survived the trip.
AH was clear what he wanted far less clear on the how it would be done and I suspect it would have proved far more difficult than he thought.
His 'plan' was for 90% of slavs to be 'removed', aka deaded, with just 10% retained as helot slave labour for the new Ayran settlers in the East.
And that gives you some idea of how utterly devoted from reality his plans were. He clearly didn't have a clue just how big the east and Russia was… mind you, neither did his army. He never seemed to have any thought were his hundred million spare Germans were going to come from.!
His early attempts at a spot of ethnic cleansing to produce New Germania in the East merely resulted in huge numbers of locals taking to the woods and joining the Partisans.
And even when he did start resettling Eastern lands with sound Ayrian stock… the Herren often weren't terribly impressed to find they were given land that was little moved on from the Middle Ages.
A series of complaints by German settlers in very rural Poland was dealt with by sending said settlers to KZ camps to encourage les autres.