I have
Word of God on this one:
David Gaider: "He's very sweet. Poor guy, goes through life, he's at the Ferelden Tower, doesn't realize he's surrounded by blood mages. Goes to Kirkwall, doesn't realize he's surrounded by blood mages. Gonna end up with a little bit of a complex, he's like "Wow, I'm a
lousy Templar!" ... I could have plans right now and "Yeah, totally, we'd have him in the party and everything!" and then next week that would change, so I'm always leery of making promises. I like Cullen. I joke about him in some ways but I like the arc he represents. There are some minor characters, like Sandal for instance, I like the idea of having them be a unifying factor. Like R2D2 and C-3PO manage to make their way into every sort of plot. Every major story has the Maker's witnesses, who witness the big chances that are occurring, a bit of connecting tissue between the games. And there are things I think can be done with Cullen.
I like the idea that he has confronted probably the worst that the mages have, he's encountered the worst of what mages can do. Yet he hasn't done what some Templars have done, like Meredith, or--I keep wanting to call him Knight Divine--Lord Seeker Lambert in the novel, how they have reacted is to become very anti-mage and very judgemental and to paint all the mages in the same basic plot, a few bad apples spoils the bunch.
Cullen to me represents another side of Templars which is a side that we need to keep active. Not all Templars are these heartless bastards who would happily torture mages, that's not true, there are Templars who are good people. I think Cullen is a good man who recognizes that there are dangerous in magic, dangers that have to be dealt with, but he doesn't lack for compassion and doesn't try to say "Well, let's take the hard approach and kill everybody and let the Maker sort them out." At the end of DA2 he's the person who sort of tries to put on the brakes, the voice of sanity if you will. I think that's important to represent, so in that respect I like the idea of Cullen reappearing, I like that element of his character, so it's definitely a possibility."
Hope that sheds some light on things.