Just realized I mentioned this in the call that was going on during the stream but not here.
As a Crusader Kings sperg I can confirm that Jace had successfully doomed his dynasty within the 10-20 minutes he played the game. See, Crusader Kings isn't about kingdoms, it's about people and dynasties. When jace chose the holy roman empire, he wasn't playing them, but their emperor. When he sent the emperor into battle against one of the most powerful duchesses in the HRE (who was only rebelliong because he tried to arrest her for practically no reason) he got his first character killed at the ripe old age of 16, his only heir being the sister that he married off in a normal, non-matrilineal marriage, meaning he successfully doomed his dynasty. Only way to recover from a failure that stupendous would involve a tremendous amount of intrigue, the assassination of at least one husband, and marriage to someone far below her already-mediocre status as a minor duchess in the HRE. It would take several generations worth of careful planning and politicking to successfully reclaim what he was handed on a silver platter at the start of the game.