For one thing you're overestimating the influence of the Khazars if you think there's a historical reason for any of them to be in the 1066 scenario. They disapear from the historical record rapidly after the sack of Itil in 968. It's probable they survived that event as a political unit, but by 1066 they were not even a Baronial-level power. If we need Jews because there were Khazar remnants running around we also need Zoroastorians, heck probably some Roman pagans too
Which leaves Court Jews and a County.*
You seem to be underestimiting the technical difficulty of including Court Jews. Here's the problem, and it's one that appeared in CK1: they never got married, so they had no kids. Even if they'd been equipped with their own marraige AI (as Baron-level characters may be) there wasn't exactly a sizeable population base to start with. Why bother with a single man-hour of work on a religion that's gonna dissapear after 30 years of gameplay? I don't neccesarily agree with this decision, but I understand it.
Now we're down to a County. If it was just the County you might win, but remember those Court Jews. If you're including the Ethiopian Jews you can't justify not including Court Jews, which means you have to add in special marraige AI (or they'll die out) and make it smart enough that it doesn't marry every Iberian Jew to an African on the first day of the game. And you've got to add the work they're putting into every CK2 religion, including lots of Jew-specific events for those Court Jews. Sounds like a couple man-days, minimum. From a really good man. Give it to somebody whose not really good, or demand specific events for every High Holiday, and we're talking man months. That's got to be 2%-3% of the development budget.
Nick
*Capitalized, incorrectly, because I can. What can I say "I feel petty, oh so petty..."