The composition adjust feature on the K-1 only moves the sensor by a couple of millimeters or so, only enough for very minor perspective correction. I own the Rokinon (Samyang) lens, and I like it quite a lot, but it does have significant barrel distortion, so for architectural work you would want software capable of correcting that distortion when the lens is shifted. I gather that there are a couple of options, Capture One being one of them.
The Canon and Nikon t/s lenses are reputed to be excellent; they also cost around US$2,000 each. As much as I share the OP's preference for getting it as close as possible in-camera, there's a lot to be said for stitched panoramas for architecture.
Last edited by baro-nite; 12-18-2019 at 09:55 AM.