Jews were sometimes hired as land managers for lords, who were off at the court of their liege, and, lacking the teleportation system present in CK2's medieval Europe, could not properly oversee the land they held title to. So, perhaps a mechanic could be developed where Jewish courtiers could manage a title, but not truly own it. Their stats would be used in place of the true owner for that particular title, making it a useful strategy for if your current character has bad stats. It could be balanced by an increased rebellion risk in that province, with the rebellion having the goal of removing the Jewish land manager, and the rest of the local Jewish population. Then the player would be in the position of being able to potentially disrupt this persecution, which is almost certainly better for Paradox than the player being on the other side of things. (It would have to be a landed title, obviously.)
Yes, it is a mechanic for Christian rulers with Jewish courtiers, not players playing Jewish characters, but I think the game would benefit from an increase in interaction between different religions beyond war (and conversions).