Again, if Charles is instead killed at Tagliacozzo, the future pope loses much of his leverage over Conradin and the Hohenstaufen, but since Swabian is no longer in Conradin's possession and the Imperial throne is currently vacant, Conradin doesn't represent as much of a threat to Rome as his grandfather had. There would be hard feelings, but I think in this scenario, a peace can be made with the promise that all sides swear an oath to go on crusade, and Conradin can marry a Capetian bride. Conradin probably must agree that Swabia is no longer a Hohenstaufen possession in exchange for being recognized as the true and rightful King of Sicily.