I'm actually quite happy with my 28-105 lens on the K-1. I'm impressed with it's picture quality ..even though I suppose it's classified as a kit lens. It reminds me a bit of my 18-135 which I use on m ASP-C cameras. It's another kit lens and also impresses the heck out of me. I recall being hesitant about getting a 18-135 as there were some who said this lens wasn't the best. After having one, I have to disagree.
Anyways back to the question at hand. I also find my 40mm and 70 mm Limited very good on the K1, which I set to Full frame, even if the lens is supposed to be ASP-C design. I don't notice very much if any vignetting with these (40,70) or other issues on the K-1. Maybe I'm not discerning enough.
So the 40,70 and 28-105 I would be able to get by with, if I found one welded to the K-1 body one day.
I'm thinking about the Pentax 100mm D FA WR F 2.8 Macro lens...it's full frame, metal body, nicely rated. Seems like a nice Macro/portrait lens for the K-1.