I don’t intend to chuck my crop sensor. I will probably use it for road trips and photographing landscapes. But, I plan on doing more studio work. I want to create photographs to hang in my apartment and also to sell on canvas or as metal prints. I intend to invest more in lenses than the body but I would like a full frame for that purpose.
I did consider mirrorless but since it will be for studio work I don’t care about the weight and size so much.
I think I am leaning towards purchasing an older Mark 5 or 4 as you suggested or maybe going to Canon’s site for a refurbished camera. I once bought a refurbished camera and it was fine as were the refurbished lenses I’ve purchased at times.
I read that since refurbished are inspected so closely when fixed that sometimes they are less risky than a regular purchase.