re: What would’ve happened if Britain had surrendered in WWII?

Lots of reasons. Muslim leaders were generally closer to Nazis than they were to the British or the French, due to colonial resentment, and didn't have the same sort of historical associations with power that developed with Jewish people or the Roma. The story also goes that Reza Shah changed the name of Persia to Iran (it's internal name for millenia) because the Persian Ambassador to Germany was inspired (supposedly) by fascism.

The scale of a "Muslim" question would also rule it out such an undertaking, as the logistics, organization, and efficiency required would be massive. At this point, it's just the fever dream of Wehraboos who don't understand human scale.

Hitler (and broadly, the German right from the fin de siecle onward) was obsessed with lebensraum and competing with France and Britain. If Nazi Germany had won, would they have taken (and exploited to the same degree) France and Britain's colonial possessions? Almost certainly. But it's unlikely that they would pursue a "Muslim" question, when historical animosity had been directed westward since industrialization.