My only problems with the KP are the rear AF buton, it's a bit up and I keep pressing the green one for focus, the missing non locking option of the mode selector and that I preferred the grip on my K-30.
But I had that camera for 4 years, if I only pick my K-30 in 4 years I will probably prefer the KP grip. (and it will probably only shoot black picks with the now moribund K-30
)
After all that time with the K-30 and 20k pics and only 300 pics with the KP, my only reason to buy a K-70 would be price, a KP at minus 200 or 300€ would make this decision an easy one (that it was for me), the K70 is really competitive, especial if you only look at the end result, the pics, but the KP was an upgrade in every level. (the k3ii is also a big variable, but I really wanted the tilting screen, size and all the small upgrades they added to the KP and really didn’t care about the major absences, battery, burst and 2nd card etc)
My preferred grip is also the middle one, I think the bigger option will very handy with the vertical grip. (Having this option is for me brilliant)
I went for the OP/TECH wrist strap and sling, still on the initial experience, but liking the freedom it provides.
(sorry for the lousy mobile pic)