I think part of the fun of GFX is really 1 lens system that can do 2 things, street photo + Tech Cam .... I am thinking more like Contax 645 lens with a 'coming soon' electric adaptor, and adaptor on Combo Actus GFX for tech cam use... which I currently adapted to do... It's not perfect yet. but it's quite fun. Lightest weight possible...+1 !
get a second hand Arca RM3D or Alpa or Cambo and a refurbished IQ150
or get a D810 (or wait for the D820 ) and 19 PC-E + 45 PC-E + 85 PC-E
The nikon solution isn't the best IQ on the planet but so easy to use and carry
Buying new gear to adapt stuff... so much money for with it is... and no capture one support !
Still the GFX is a really good solution if you don't need movements.