That’s quite a versatile setup (from extreme wide to telephoto). Makes me wonder what your main photo genre is? For which type of photography do you use the fish eye lens? I don’t know anyone that has this “exotic” lens.
In answer to your questions......but firstly I admire your kit, well thought out, all practical ergonomic for the purpose, and light which i like, its focused on photography.
My photography genre is spontaneous, always wide and varied, sports action, paparazzi, creative, wild life, nature, land, sea scape, street photography, travel, commercial, its endless and different all the time, this makes it hard to invest in more specific or exotic gear without ending up with my own camera warehouse LOL.
So i need a broad basic kit that covers 14mm to 500mm without to much duplication or excessive amount of gear.
I am also of a wholly trio plus school and believe
less is more, 14-24, 24-70, 70-200, add a 200-500, hire anything else.
My vision going forward is i am attracted to smaller lighter, one day, hence i like your kit for what you do.
I am waiting to see what the Z8 has to offer, if it has at least 12-14 fps is small light like the Z7II then its good bye Z9 in a heart beat, i am not defendant of auto 3 D tracking.
If i cant nail what i want with what i have i need to question how and what i am doing.
I find my D850 to be the best do anything well all round tool, with image files i just love. Its not a Z9 dedicated in tracking and speed etc.
The Z9 i have is a toe in the water of mirror less, yes its larger heavier, similar image files to the D850, it offers for me at 45mp a OPTIONAL significantly higher frame rate and
the key advantage of super fast focus attack speed, the rest for me is optional or in cases overkill and
to complicated to enjoy, but that's me, some like a Muscle car others a Toyota Camry LOl.
If i have special purpose needs or doing an important project, i hire the likes of a 600mm F4 or a D6 or whatever.
Some days I can be covering a Surfing competition finishing around late afternoon, and could finish with a seascape with sunset, or birds in flight in golden hour.
If i am traveling in the van (bed on wheels) LOL i like to be prepared for anything any time.
For me in my kit i cover 14mm to 500mm, my mantra is
"I paint with light, the lenses are my brushes nothing more or less"
16mm F2.8 fish eye...........Its a stunning lens, very sharp, has a
180 degree filed of view, brilliant for Astro, landscape, seascape, and especially creative photography, street photography, my friend used 2 of them on DX cameras to do a creative wedding shoot, an amazing lens if you know how to use it to its potential.
It comes with 3 small filters, each one can slip into the back of the lens, red yellow clear, brilliant for black and whites. Wont focus on mirror less cameras, becomes manual only.
It was made originally for Astro many years ago, its super tiny and light, its unique and a bit like the 19mm Tilt Shift to use, that lens is as good as it gets for ultimate sharp landscape architectural shots but you also need to know how to use it to its potential and harness its magic.
Only an opinion