Are they going to consult Harry Turtledove for script ideas? He wrote several books on a similar premise.
Or the Draka Domination by Stirling, featuring uber-Nazis so bad the Nazis are fighting for the good side, humanity.
Also moves into the 1970s with spaceships and slavery, while the stand alone novel Drakon features genetically engineered slaves, engineered masters with total domination except humans who fled to another solar system.
Guns of the South is a great book if you are 23.
If anybody ever invents a time machine, I’m stealing it!