Tokina just announced the Tokina 400mm f/8 reflex MF lens, which you can use on any Fujifilm X camera with the Tokina Mount Adapter TA-014 for Fujifilm X.
Fujifilm X shooters living in UK are definitely lucky.
Not only they get the fastest repairs (as the EU service center is located in UK) and can visit the Fujifilm House of Photography (a worldwide Fujifilm-unique store, where you can already admire the Fujinon XF50mm f/1.0), but since this year, they also offer totally free 48 loans on basically all X and GFX gear (including GFX100).
I hope this is something that will get extended to other countries too.
What would I rent?
Well, for sure a Fujifilm X-Pro3, and just pass 2 days photographing with it and see how it feels to shoot with the hidden LCD screen, and without a doubt also the Fujifilm GFX100… you know, just to hide in some corner at home and pass a few hours pixel peeping and cropping like crazy ;).
In terms of lenses, I’d surely rent the XF100-400, which is something I am lusting after for some wildlife shots in my mountains and then the GF23mmF4, because, you know, with that GFX100 all you need is a wide angle lens and then you can just crop endlessly into the image.