Sony A7RIV, FE 28-60
OK, so we covered crop options for Landscape/Hiking/Video uses.
Now let's do Full Frame.
First up is Canon. This would be a re-buy situation to some extent, as I just sold off my Canon gear. I'd definitely rebuy the RF100-400 and probably the 24/1.8 as well. I'd want the new 16-28 or the 14-35L and some mid-range option, plus a macro (likely the 100L in EF mount). Body would be either the R6mII or an OG R5. This would work pretty well for this, but I'd still struggle a bit with the lens line overall. Plus the limitations on assigning Bracketing to a button would annoy me just as it did on the R7 and R6. Possible only if I got a screaming deal on the body. R8 is an option for light carry here too (but limited/no IBIS and small battery).
Second is Sony. The most wide-ranging lens lineup, most lenses can be readily adaptable to my Z7 via the MegaDAP ETZ21 Pro adapter, and my partner still shoots an A7II. The downside is which body. The A7IV and A7RIV are really the two options here and I don't really gel with either of them. If forced, either would work adequately though, so I wouldn't be unhappy, just occasionally annoyed (especially with the Dust. Why hasn't Sony figured out sensor cleaning yet....).
Third is of course Nikon. There's two real problems with Z mount for me. The focus is on long lenses, not wide (and mine is the opposite) and none of the bodies quite fit my needs or wants. The Zf and Z6III are acceptable though and I could probably get away with either adapting some FE lenses on the wide end or getting the 14-30. One annoyance here is it seems Nikon is dead set on ensuring you have every single possible different filter thread you could possibly own needed for their lenses. Only the Tamronkors have consistent thread sizing (the 17-28, 28-75 and 70-180 are all 67mm).
The wild card is Panasonic. Over the last couple of years L mount has emerged as a real contender since finally introducing PDAF and addressing the AF issues for action shooting. They're still not top-tier AF, but they are at least as good as the non-stacked sensor Nikons. Plus the lens options are excellent and pricing is aggressive. The S5II covers my needs for a 24MP hiking body, and I can easily and relatively inexpensively put together a kit of 20-60, 100-400, 100 macro and 1-2 f1.8 primes, and every single lens on that list has 67mm filter threads. The bodies are very customizable, the S9 works as a light carry/B-cam and I have access to the top-tier Sigma lenses if needed (plus Leica if I want to be insane). The only real lack is high-MP options, and they're there just not cheap. The S1R update however should drop prices of the original and that would give me a 47MP option for tripod shooting. Plus the ability to load LUT's and apply to JPEG's gives the possibility of my post workflow dropping dramatically (you can convert LR presets to LUT's, then load onto the S5II, the S9 and the upcoming S1RII). Also the S5II costs as little as a Zf, except it includes the brilliant little 20-60mm in the package (and often adds the 50/1.8 for a very small upcharge). Get the 2 lens kit (20-60+50), add a Sigma 100-400 and the tiny and excellent 100/2.8 macro and I'm set. I could add the 18/1.8 later for a native fast UWA too.
End result, Panasonic seems to cover most of the requirements. Nikon is #2, Sony and Canon both viable if the right deal is found. Clear leader, but unlike in Crop, none of the options actually fail out.
