Animals that might be candidates for full domestication and why

I’ve had them, too. If they’re raised well - like dogs! - they make excellent pets. Unfortunately short-lived, as you mentioned.

They are completely domesticated, descended from an existing wild species:


ETA: to answer the O.P. more directly … snow leopards, or maybe clouded or marbled leopards, would be gorgeous pets … but, damn, they do need an enormous amount of climbing-type exercise.
Perhaps a domesticated pet could accompany its owner to one of those urban indoor rock-scaling gyms?