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Nothing wrong with using it on m4/3.
It lose quite a lot of character of R lens. Those m4/3 prime will beat even Leica modern M with 2~3X sensor density on 1/4 of FF sensor. and I can safely say you will not get similar shot as your nice portraits shown here with m4/3.
Keep in mind, you can pretty much convert any Leica R lens to your Nikon save for some extreme ones (check Leitax website), but you will not have coupling between lens and body. That means, you will shoot in stop down mode, what you will see is working aperture you choose. This can be a problem for stop down shooting sometimes. Also, you will not have EXIF data to show correct aperture. All WO, though it is still better than Canon without option even enter focal length and max aperture.
If I were you, I will not save dime on converter, Leitax is great. It fix my aperture problem of Leica R with cheap F mount I bought. Before, the aperture is very soft and uneven, with virtually no f16, now with Leitax, it perform beautifully.
Hope this help. If you don't mind focus ring turning direction and enjoy high quality manual glass. ZF.2 is hard to fault given its performance on pretty much every focal length it released so far. Especially consider R lux and APO lens used price is really high to swallow. Most focal length, ZF.2 offer close to even (better here worse there) performance with cheaper price BN. Only miss longer than 135mm and APO stuff.