I taped a 3" Hoodman loupe to the back of my K-01 ,,, see
https://www.pentaxforums.com/forums/138-pentax-k-01/232295-will-vf-3-view-fin...ml#post2461637 ... and, with the inexpensive but VERY sharp Pentax 35mm f/2.4, I'm extremely happy. Carry it around all the time... which is saying something, since I also have a Sony RX100, also a very good camera. But the K-01's my favorite... it just feels good to use.
Let's see ... one other modification ... put a little piece of gaffer tape next to the on-off switch, to stop it from turning on accidentally. That's actually the only thing I'd change about the K-01... just add a bit more tension to that switch.
You can use it for sports without any problems. It's easy for most sports to pre-focus where the best action will be. For airplanes against the sky... not so good. The auto-focus will hunt back and forth and you'll miss the shot. For situations like that, get a K-30 with the 55-300mm lens.