Oh I'm not gonna argue about YONS being a terrible challenge. Any challenge that requires insane amounts of powerlevelling for a boss is dumb, and this one takes the cake. NSGNSxxx challenges are fun, because they are about using the right strategies. They may require item hunting, but that's different. I've also always been a proponent of just customising a Phoenix Bracer if Greater Sphere doesn't drop it right away. Mindless repetitive grinding is dumb and doesn't add anything to the overall experience.
I remember when I played Wakka Only No Attack Reels challenge, I broke the NAR rule on Anima. The choice was either grinding for hours, then rolling all over the rest of the challenge just so I could kill Anima in 2 or 3 hits, or keeping the challenge alive for the rest of the game and not spend hours in Macalania with a boring grindfest. I didn't even have to think about the decision. And Wakka grinding is still significantly faster than Yuna grinding, as he does approximately 10 times as much damage with his physical attack and he won't miss birds, lizards and wolves 75% of the time.