Axis
- Melting pot strategy instead of racism: Much more people, much better science&tech, much less flow of information and professionals to the Allies, Einstein may stay in Europe (maybe no or later nuclear bomb), more support of the people of occupied territories in the East, and so on. A few minor changes are necessary to get the same increases in production.
- Competition instead of synergy: The Nazis increased production and productivity by combining companies of an economic branch into huge monopolies. That gave them gains due to economics of scale at the beginning, but later cost them a lot due to less competition. Prices needed to be fixed, for instance, when the war production soared, which made it difficult for the economy to adapt to scarce ressources. If competition had been enforced (partly by more international cooperation during peace times), that would still have allowed economics of nearly the same scale, and more longterm growth.
- More subs, to allow an effective war against British shipping in case of a war against GB.
Allies
- Quick development of tactics against German tanks after the Nazis invaded Poland and their strengths became obvious: Molotov-Cocktail, Artillery against tanks, ambushes with tank mines, and so on should be possible to figure out and train within the weeks the Allies had.
- An offensive against Germany within the first few days of the declaration of war, to quickly gain south west and western Germany.