Which version of Cooper? He was very hot and cold. In real life, I doubt it. In the idealized ESB H2H world where we take Cooper from that one fight where he was on fire ... sure, why not?
If everyone is fighting at the top of their game I believe the only man Cooper beats is Galento. I believe Bert has more skill than Tony and Cooper is a guy whom Galento wouldn't be able to out-tough.
If you ran Mercer fight Cooper through that lot enough times you'd get an occasion where he went 5-0.
No. Cooper was never that consistent against top competition. Also, if all of the guys are in top form Cooper likely goes 0-5. Although Cooper had the talent and ability to compete with anyone and even be a champion, but unfortunately was his own worst enemy.