Biggest thing is wondering what to do with her and the seekers and the divine issue. I'd rather not give her to those chucklefuck orlesians. They don't deserve her. But at the same time, I don't want her resenting me for not supporting what she herself wants to do. So I'm more inclined to make her divine.
Her romance card stays the same if you don't break up with her and she's made divine, so like you all for Solas, I still have hope for the future despite the initial split up.
I love Cass and that is why my inital impulse was not to make her Divine. Because I do not think she wants it. She wants to see change and is willing to fulfil her duty of bringing it about if need be. But she is a soldier at heart and not made for all that political intrigue and hogwash. I feel affirmed by her own reactions. When you ask her if this is what she wants she does not actually answer as she usually would, instead she comes up with some pseudo-answer along the lines of "Does not matter what I want". Also, when you tell her that there are other ways to change things she approves.
What she wants to do is rebuild the Seekers, and I think that is what she should do.
If she went to be Divine it would mean a lot of hardship. Also because she would face the cold truth that some things cannot be changed and that some attempts are in vain because you do not always hold all the strings in your own hands (just see the mess in Kirkwall). I fear this might even shake her faith.
(Also, the epilogue with her as my Divine was not so satisfying that I want to put that burden on her... "not worth the sacrifice")
Alight, I don't make Lelianna Divine anymore. For a very simple reason, which is this one line she says. "People are sheep, they need to follow" (or similar). That is awful, that is my absolute no-go. She assumes that people are uneducated (or rather even dumb) and instead of educating them she just wants to dictate what should be done. I do not support a dictator Divine. Our world has seen enough people who believed to know what's right and that people just have to be led into that one correct direction. We know what comes from this sort of arrogance. Unfortunately, I just found out this side of her when I did not support her in my second playthrough (but the first should be my canon because in real life I also cannot just go back and change my decisions).
I am not so sure about Vivienne. 50:50. She wants to restore what was (and since Solas wants the same, probably this is the thread-appropriate choice), with slight improvements (okay, maybe not so thread-appropriate). I really don't know where this will lead us. She is, after all, the first mage to take that title and this alone is worth a lot, I guess. Could improve things for all mages in a more subtle, more elegant fashion. And because I am not sure there is so much potential in her, so that's why I suppose she would be my choice.
(Actually, I only supported Lelianna in my first playthrough because I had allowed someone else to decide this one bit. I had considered Vivinne right away, because I did not want to burn Cass and I did not fully trust Lelianna.)
In the end, it all will come down to the same mess anyhow.
Yay. My longest off-topic post ever.
Sorry.