I actually think this would be really fun to watch. Some fights with the contenders like Buddy, Nova, Godoy, Galento, Uzcudun, etc; would all be really entertaining scraps. He can win and lose them. I think Nova and Buddy beat him, but I wouldn't be surprised if Jirov turned the trick. He can definitely win the title, too. Vs the right guy. Braddock, for example, I think would be out-worked badly by Jirov. To me, Jirov did well enough vs Toney to where I'd pick him to beat an ill prepared Sharkey, so that's two champions I'd pick him to beat. Carnera is another who I can see him beating, but I'd probably pick Preem. Jirov was about as hittable as a piñata without a blindfold. That doesn't work vs Max Baer. Look, Baer isn't Pernell Whitaker, but he also wasn't dropped by any middleweights. I just can't see Jirov applying so much pressure and not getting levelled by that overhand. Max Schmeling is about as bad as a match-up for Jirov as there ever was. And Louis would do something seriously scary to Jirov.
Big fan of Jirov and think he'd do well against the contenders of that era but Louis would absolutely decimate him, would look something like the first Foreman - Frazier fight. Carnera would be interesting as would Schmeling.