This conversation is not making future buying choices any easier! I've been using the A7C for last year and a half, and the new FCP, although really freakin' expensive, is enticing. But the A7C R is also enticing, and also entails the new housing. Decisions, decisions. Or maybe wait till the A7C III or R II. Who knows, it's always something.
I'd agree with the 7AC, but the 7AC II/ 7AC R are generally the same sensor/AF as the IV/ RV models, but a slightly smaller case. And unfortunately, they won't fit in the older A7C housing. The biggest difference may be the strobe sync speed as I don't think the A7C II/ R inherited the 1/250 speed of the A7s.
Another transplant from WetPixel primarily diving Puget Sound and Seattle area of Pacific Northwest. Been shooting Sony for last 10 years and primarily dive CCR these days.