I agree but I'm spoiled by the m43rds weight. Therefore I would only consider f/4 zoom lenses in FF. The Sony 24-70mm f/4 is soft. That leaves the Nikon 24-70 S but I don't jump on first gen cameras. So right now I plan to wait.The a6400 looks fantastic I must say. The lack of good Sony APS-C lenses is the killer in their system though.
I think my photo future has Nikon FF mirrorless written on it.
(Fuji is too small a step up in quality to be worth the cost and hassle of a switch IMHO).