Thanks for the advice. The 85 is the Nikon G, the 70-300 is Nikon 4.5-5.6.
I’m not sure I’ll jump all the way to FF by going directly to ML. Are the lenses usable on the Z mount or is the performance degraded?
I have a D7100 and several lenses. Had planned to add an FX body for a few years but hadn't gotten around to it yet.
Was thinking of getting a D750 but opted to go ML instead. When Nikon had their spring sales earlier this year there were some good discounts. I ended up getting a Z5 and the 14-30 f/4 S and 24-70 f/4 S Z mount lenses. I was tempted to go with a Z6 or Z6ii but I needed to replace my dead 10-20 DX lens, so picked the lenses first and then the body.
I use both the D7100 and Z5. So the Z cam was not a replacement, it is a complement to the DX body. The Z5 focuses better in most cases. No need to fine tune lenses for the most part (the capability is still there in the FX Z bodies) and the focusing system benefits from the newer generation of Expeed processors. Some people even see better performance with their F mount lenses on their Z bodies - possible due to the way the focusing system works. Also better high ISO performance and less noise with Z FX compared to DSLR DX. The Z mount lenses are better than their F mount equivalents, but the F mount lenses I own or have borrowed are no worse on the Z body - no degradation in image quality, at least within the DX frame area. On the FX body you will see areas outside the DX frame that you would not see on the DX body so you may get the impression that the lens IQ is degraded, but you are really just seeing a larger area of the image circle produced by the lens. So corners and edges may not look as good. But that is the case whether you put the lens on a DSLR or ML body.
Focus speed may be a tiny bit slower on some the AF-S lenses (you have to use an FTZ adapter) but I have the AF-P 70-300E f/4.5-5.6 F mount lens (FX). This lens is much better than the older AF-S 70-300G FX lens which I also owned and just got around to selling. The AF-P version, even with the FTZ, seems to focus a bit faster on my Z5 than on my D7100, and it focused faster that the older 70-300G version.
Since getting the Z5, my D7100 is mostly used for wildlife and Zoo stuff and some action, like surfers, where I get the equivalent narrower field of view compared the FX sensor (e.g. 300mm on DX equivalent to 450mm on FX) and the Z5 for some zoo stuff and everything else.
Your 85mm f/1.8 would still make a nice portrait lens on an FX Z body even though by most accounts the Z 85mm lens is an improvement.
So you can certainly get a Z FX body and wont lose anything regarding lens performance. You will have to learn the nuances of the Z focusing system through. But there are plenty of aids out there such as Thom Hogan's and Steve Perry's eBooks. I found the transition from D7100 to Z5 pretty straight forward except some button differences.
Replacing or adding to your D7200 with a D750 would even be a more seamless transition.
One thing I definitely like about the ML bodies is that the focus points pretty much cover the entire sensor area. If you go from D7200 with its 51pt focus system to a D750 or D610 you will notice that the focus points cover a smaller area of the frame compared to the DX body. Not really a bad thing. Just different. Less focus and recompose with the ML body though.
Also, with the FX Z bodies you get stabilization for non VR lenses. An with VR lenses the stabilization may be better. Shooting with my AF-P 70-300 at with focal length set for equivalent field of view (e.g. 200mm on DX body and 300mm on FX body), stabilization seems improved - we are getting at least one additional axis of stabilization.
The thing is, I bought them for what they can do on APS-C - I've tuned my lens lineup over many years and on another format, I'd want to have something similar. That would suggest a 45MP body I could crop with or a whole new set of lenses. 
