Hi
There's a kit for everyone from almost every manufacturer, in fact by far the most important thing is to point whatever you have at something nice!
As someone who owns exactly what works for me, here are my thoughts, they may help you they may not.
I own a D800, a D800E and a Sony RX1 and love them all equally but they excel in different areas. The RX1 has beautiful files but as strange as it sounds, it is just too small without a grip, going small is not necessarily linked to usability. I bought the RRS grip for the RX1 and it is now brilliant with a built in tripod mount but without it I wouldn't have kept the RX1.
On to the A7/r, I have used the R a couple of times and for me it suffers from the RX1 issue, compact it is, easy to use with bigger lenses it just isn't for me, the D800/E sized body has a decent grip and I can move around the studio or out in the field with it simply hanging from my fingers on the grip, impossible with the Sony. So for me, the Sony is a marvel of compact technology but at the expense of being practical for the type of shoots I do. My second issue with the Sony is the lack of native lenses, this may be irrational but I refuse to spend that sort of money on a body and a Zeiss 21 or a 135 and then go to a third party company who is not supported by either camera or lens manufacturer and spend a couple of hundred$ to get everything to fit together, it just goes against the whole quality of the system, there are so many threads commenting on adapters that are too tight, too loose, need a bit sanding off, need some cloth sticking inside to reduce reflections, etc. etc. the system is incomplete without native mounts, my view. But lets say I find a great adapter, I find a grip to make the sony useable with a Zeiss 135f2 or an Otus, walking around with it I'd feel as though I'd have to cradle the camera because it's so unbalanced, I know this because I tried, my 135f2 is beautifully balanced on the D800, it's a nightmare on the Sony
I will say that if you're shooting landscapes then in my experience the Zeiss 21 is just beautiful, I'm sure it would look as good on a Canon or Nikon, I don't believe you need af at all on that type of lens, it's not like you'll be doing wide open fast moving fashion with it.
I am brand agnostic, I actually own m4/3's, I have 2 Canon bodies, 2 Nikon bodies and a Sony body, I only care that it works and would jump to another system if it really offered benefits but I have never been happier than I am with the Nikon, it just works.
As long as you find something that works for you then you will be happy, try them all if you can, good luck!
Mat