A7R II vs Nikon D750 + Panasonic GH4

I will lose my mind while deciding between these 2 combinations. Currently as a GH4 owner i am not happy with stills and want have more DOF, more dynamic range, better IQ and low noise on low light. I am also in videography. Loved downsampled video quality of 4k which is taken with GH4.

Should i sell my GH4 and buy A7R II or just use GH4 only for video and own an extra D750 for stills ?. A7R II vs Nikon D750 + Panasonic GH4