Please help me think through a possible system change. (cross post) Thanks!

A little history first. I have switched to different systems at least 5 times in my film days having used Canon, Pentax, and Minolta and switched back to a previous ones once or twice. I ended up going with Pentax in the digital era because I still had a few lenses left. I have never switched systems once without it being because I acquired a lens I just had to shoot. When Ron was alive we were all looking for a Holy Grail of lenses, the Sigma 100-300/4 EX in Pentax mount. I never found one. However I found one in Canon being sold by a published wildlife photographer. I had a Canon 20D I used for astrophotography. So I bought it. I liked it so much I ended up going thru a progression of 20D, 30D, 40D, 60D, and finally 80D currently. Meanwhile I was going thru a progression of Pentax *ist D, K10D, K20D,  K5II, K5IIs, K3II, and K-1 plus K-01 and KS-1 when they were bargains. I generally use Pentax for everything but motorsports and sometimes Canon or Pentax for nature. Like others have said it sometimes not easy to find something you want in Pentax. But for the first time ever next month I will be going out to NM to visit by brother the pro and I will be only taking the K-1. First time since the film era I have only shot FF. While my brother mainly shoots LF he does have a Sony A7 (II or III I don't remember) system he uses in place of Polaroid for sample images and video production. He is one of the worlds top architectural shooters plus he does a lot of celebrity houses in Taos. And teaching at the Art Institute of Chicago. And books on the Southwest.

My personal opinion is you need a precise purpose for a second system. It must do something your regular system does not do as well. And I mean largely better not marginally better.  Or you need a lens your current system does not have available. I have found over the years that most amateur shooters change cameras long before they ever finish getting the most out of their current system. And that can require testing.

Kent Gittings