I have to modify my initial response. Other Nikkors may produce less obvious vignetting than reported for the 50/1.2.
Thus, in a pinch, the suggested approach of using Metabones for m43, and the m43-Z adapter, can yield a lens 1 stop faster.
I shot earlier today with the 35/1.4 Nikkor, with is converted into 25/1 by the Metabones. However, I did lose the CPU linkage (my 35/1.4 AIS is CPU-modified) so the Z50 falls back to unassisted manual mode. Which frankly is implemented very badly.