And that to obtain equivalent IQ we need to turn to the
Sony FE 35 mm f/1.4 GM (524g) or
Voigtlander Apo Lanthar 35 mm f/2 (352g, MF). Suddendly the weight story is indeed a 28% increase, in a 1 lens setup...
Conclusion: if carrying only 1 lens on not caring for IQ, the Sony Alpha 7C system carry only a <20% weight penalty over a equivalent Fuji setup. If using a more comprehensive lens set-up and trying to match IQ, then Sony carry a closer to 50% weight penalty.
Sony A7C is incredibly compact, but physic is physic. Even it is true that APS-C system is not benefiting as much from weight reduction at every configuration possible as we would like, when comparing IQ, the Fuji APS-C system remain the best quality to weight tradeoff, blowing even Sony offering.