What if Schmeling and Sharkey competed in the 50s instead of the 20s and 30s? In this scenario, they'd both go pro in 1950. Sharkey turned pro in 1924 and would be one of the top heavys by 1926. Schmeling also turned pro in 1924 but wouldn't become a significant contender until 1929. That means Sharkey would've likely been in title contention by 1952, and Schmeling by 1955. Sharkey was a contender until about 1933, and Schmeling was one until 1939. This means they could've been elite heavyweights well into the 1960s. How would the presences of Sharkey and Schmeling influence the division? Can they win a title?
They would have crossed paths with Marciano in the early to mid 50s and either Floyd Patterson or Sonny Liston in the late 50s. There's a good possibility that Schmeling may have dethroned Floyd Patterson like Johansson was able to. Sharkey would have been competitive with Patterson, but he didn't have the punch to stop Patterson. He may have dropped Patterson, after all, he hit hard enough to drop Carnera and Patterson was dropped by Roy Harris and Pete Radamacher. If Schmeling and Sharkey ran across a late 50s Liston, I think Liston would have eventually stopped Schmeling. Schmeling did upset a near peak Joe Louis, so it's not beyond all possibility he upsets Liston, but I'm not sold on it. Sharkey, if he boxed smartly, may have made it to the end and lost a decision. But Liston could have stopped him as well. Whether the early or late 50s, Schmeling and Sharkey would be top contenders.
I am really not sure if either of them could have secured the Lineal Belt then, but I do believe that Max Schmeling would have had the better chance of the two.