So I figured out how to view the traits/ancillaries spreadsheet. Very, very impressive.

I was thinking that expanding on the 'Eleusinian' trait model would be cool- there were other cults that were popular, especially later on in Rome; Isis, Osiris, Dionysus and later on Jesus. Don't know if that will offend anybody but the christians were seen by the Roman establishment as a kind of jewish cult.
The icing on this particular cake would be Divine Rights given to faction leaders. This could be a trait in two ways: if you had a particularly successful faction leader you could have him 'Worshipped as a God' with huge bonuses. And that trait could trigger a 'Cult of Augustus' (whoever) style trait in family members that come after him.
Perhaps 'Worshipped as a God' could have influence, public happiness and law bonuses but decrease loyalty in some generals (jealousy)?