Sainthood is not in the game. It was in the first Crusader Kings. If they create a dlc for papacy/catholic faith I think this might be something they might add in it.
Yes, the good old time when your forefather was a saint! But this is linked to the following quote, so I'll answer to the two:
and papal controller too!
When studying in university, I learned there was clearly a political aspect to canonization, which was used as much as possible by every noble family in Middle Ages: every noble family tried to have a saint amongst her forefathers, because this was a great source of prestige (didn't I saw that word in CK2?

). No need to explain what the use was for this prestige: alliances, marriages, clerical jobs (bishops, abbots, canons and so on, so much more jobs for the family as well as consequent revenues).
And families put the Church in constant pressure to have a saint reckoned amongst them: you could then found a monastery, which would prey for the saving of their souls... and evidently receive estates, lands, villages, treasures and other valuable goods which could be managed by a secular member from this same family (the 'advocati', something like 'defender' or 'lawyer'). This was clearly a way to use Church wealth to the benefit of the family, for their own use, considered as a payment for their services.
The situation was very different, following places and periods, but would be so much interesting within a Clerical DLC.
You do in Catholic and Orthodox religions. In fact you have to be not just dead but in heaven. Other religions may disagree.
Just a question, not sure about the response: is it the same with islam? For what I know, there are:
- imams, which are considered as doctors of the laws, very pious and so on, and so receive the mission to guide the muslim community to the salute;
- some real important people, considered as saints without the term. I know there are Shiit saints (others than Ali, Husayn, Hasan and others amongst the most known), revered by Iranians in Syria (in ar-Raqqa, for example); I know also the case of Mehmet II, the Turkish sultan who conquered Constantinopolis. I saw his tomb last year in Istanbul, and have been deeply impressed by the devotion of the Turkish people towards him. Something like a saint, I believe, even if this word is not officialy used in Muslim word.
If anybody has more information about this question...
So: I think all of these aspect would be great within CK2, in a way or another. But seems the disappearance of saints from CK1 to 2 may be a sign something will be done about this.