Inoue would be biting off more than he can chew moving up to 126lbs IMO, if he was a bit slicker, I could see him being able to move up even more, yes he can box, but he would have to fight Ball off at times, and his power has to give some point if he keeps moving up, and Ball is stronger, I think Ball would outhustle him to a decision.
The Fulton that outboxed Figueroa could very likely give Ball a tough outing. Wouldn’t mind seeing this at some point.
Fulton would definitely give Ball a run for his money. I'm not entirely convinced that Ball is that much better than Figueroa or even that he hits harder quite honestly, and the Figueroa that Fulton beat in the first fight was at the top of his game. I think Ball would get very frustrated by Fulton's inside fighting and would probably get a couple points docked for shoving him too much (or kicking). Doheny's a hard man to look good against for anybody but it was discouraging to see how hard it was for Ball to cut off the ring on Doheny and how successful Doheny was in finding counters and outmuscling Ball on the inside. Ball has a temper to him and has a bad habit of losing his composure and fighting dirty. It wasn't Inoue's relentlessness and pressure that broke down Fulton, it was Inoue's methodicalness, his ability to outbox Fulton and take away his tool-kit, that's what won him that fight. Fulton is a very good matador and Ball is a very capable bull who has shown flashes of brilliance but lacks composure at times and has some unrefined aspects to his crafts. Fulton is, overall, the better boxer and more versatile but the main question mark which lingers over his ability to win this fight is his ability to deal with the physicality of Ball. Currently, I'd have Fulton as a favourite to win.