Zeiss Ikon designed the Nikon RF cameras so nothing innovative there apart from slight modifications. The Nikon F is essentially a rangefinder with a mirror box, just as the Zenit C (S) was 4 years earlier. The irony is modern Bessa and similar rangefinders from the same factory are based on a Cosina SLR minus the mirror box and prism.
Innovative designs where the Prakitana and very early East German made Contax acemeras and then the Pentax S.
My own feeling is the Leicas didn't mature until the IIIf & g and the M series was already in the pipeline evolving fron the IV prototypes made before WWII.