I think any professional FF camera is capable of making great images. My feeling is that the K1 Mk II is too limited with respect to lenses. Sony has great potential but needs another generation or two to fill out the system and allow complete in body sensor shift (without software). Nikon and Canon have been too conservative and are significantly behind. We shall see if they can pull a rabbit out of a hat and blow us away with their mirrorless prowess. My recommendation would be to wait until the fall and see if any new professional quality mirrorless system come into existences, then make a move. If you must make a move, I’d recommend any of the 40+MP FF cameras with top quality prime lenses...
In-body pixel shift may seem convenient, but, ultimately, causes more problems than it solves. Doing it in post-processing gives you much more leeway to deal with subject movement - rustling leaves or grass, moving water, even clouds. You can simply mask out the affected areas and cover those with a single-frame image, while using the pixel-shift image for all the static parts of the image. But, if pixel-shift was done in camera and you didn't have the individual component frames, you wouldn't be able to do that and would be stuck with the motion artifact.
For landscape photography, I find that prime lenses are a trap which can just as often reduce your final image quality as improve it. When shooting landscapes, you have little control over the focal length you need for any particular shoot. If you want a particular composition, you need to shoot from a particular location - you can't move trees, mountains and rivers so that you can stand somewhere more convenient. 'Foot zooming' changes the composition, and, even if that isn't a major issue (e.g. if the scene is all background, with no real foreground elements), is often physically impossible. Therefore, there are only three ways to get the angle of view you need - crop, stitch or zoom. Stitching is ideal, but often impractical (wind-related movement being the bane of any landscape photographer). Cropping from a wider lens costs you valuable megapixels. Zooming to the required focal length allows you to get the desired angle of view in one shot, without cropping, but is obviously not possible with a prime lens. And it is not often that the required angle of view corresponds exactly to a 24mm, 35mm, 50mm, 85mm or 135mm lens.
Given that you're likely to be shooting stopped-down, there is minimal difference in image quality between a good prime and a good zoom, even when using the entire frame. There may be some differences wide open, but you're unlikely to be shooting most landscapes at f/2.8. And, since, with a prime lens, you'll be cropping almost every time you can't stitch, you end up losing further image quality, that you wouldn't lose had you used a zoom that allowed you to use the exact required focal length in the first place. If you need 168mm f/8 for a shot, a quality zoom set to 168mm f/8 is going to beat a 135mm prime cropped to the same angle of view every time.
