In a pie-in-the-sky world, I would be following up my Pentax K1 II with the HD versions of the original "three amigos" - the FA Limited primes at 31mm, 43mm and 77mm. They are not cheap but not all unreasonable (the HD version of the 43mm costs $500 new right now, on a sale that seems to keep sailing along, so to speak). I think it's only fair to match the quality of the sensor and build of the K1 with lenses that have the same attention to detail, as well as some "magic" qualities to their rendering which I have to admit I can see some inklings of in the images I'm browsing. In other words, it's not all in the eyes of the beholder. The 31mm, especially, has amazing bokeh for a wide angle, and the smoothness of the transition zones from in-focus to out-of-focus are really impressive. I think most modern lenses are built for a kind of clinical sharpness from edge-to-edge which seems to sacrifice the smoothness of transition zones. Likewise the 77mm has really pleasant transition zones and is a really useful focal length (I used a nifty fifty f1.8 on an APS-C DSLR as almost my exclusive lens for several years once upon a time). The 43mm is probably the least "special" of the three but is the smallest, almost a pancake, and is very sharp and versatile. Its bokeh is not quite as good but it's billed to be a photojournalism lens, amongst other things, so clarity and directness of rendering are what they seemed to be going for with it.
I am very tempted to snatch up the 43mm first, but is that at all practical? Nearly everything I have is around the 40mm range, it's a favorite of mine. The 40mm GR is always ready, with as excellent of a sensor and optics as anyone could ask for. The 77mm would actually put a nice short tele into my current lens stable. The 31mm would be probably the best buy I could make, but is typically the most expensive. And SMC versus HD is probably not that big of a deal. Although Ricoh just announced a strange sort of seasonal firmware update which is basically a promotional for their HD Limited lenses only. If the price difference were not too great, it might be fun to try out these custom tailored JPEG modes as they are released.