I don’t really need a full frame camera. For what I do the APS format works out great, I can get up to 600mm equivalent from an affordable lens and not break my 70 year old neck with massive weights.
I did that with my Nikon FE. Motor Drive on, SunPak 'Potato Masher' flash attached , and a big honking wide angle zoom lens on it (batteries for everything weighed about two pounds /s). Maybe that's why I have back problems today? ;-)]