Ruiz vs Ortiz would be fun for me so that Would be my pick. I wouldn’t mind seeing him against Parker or Usyk or even Joshua III provided he can lose 15-20 lbs and negotiate a smaller ring size.
Ruiz should still have a decent amount of options ahead of him. His chin and hand speed, and decent pop makes him a tough and competitive fight for any of the top 10. I always thought he was a tough fight for Wilder for example, despite his disadvantages - the ability to move the head and get inside, with a good chin and fast hands makes him dangerous for Wilder, who likely can’t neutralise the pressure with movement in the manner that Joshua did, as his footwork leaves a lot to be desired. Ortiz would be a fun fight as many others have said. I could see him beating Whyte, but Fury likely embarrasses him. I like him against miller too. He matches up well with a lot of them and I would be intrigued to see any of these fights - Povetkin and Hunter included.
He settles into a nice career as a gatekeeper/occasional title contender now that he’s got the “former world champion” tag on him. His profile is certainly much higher than it was going into the first fight when no one gave him a chance in hell of winning.
He is going to remain a hungry fighter and his weight will balloon. He might fight 2-3 more times and then retire with a loss.