I still don't know how to feel about Setsuna/Marina. It's obviously a key relationship, but I'd like to think that they're going to leave it ambiguous and...pure rather than simply hook them up in the movie. With Saji and Louise as the Main Couple, in Gundam 00 the creators are free to be much more ambiguous about whether the hero ends up with anybody.
Setsuna/Marina has a lot of the delicious ambiguity that normally draws me to a pairing. I think there are two factors at work preventing me from shipping it wholeheartedly. One is that I read Setsuna as intensely asexual. The other is that the show never really convinced me to care about Marina--although she's an interesting character to write, when I do write her. I understand that they meant her to be a subversion of the now-typical Powerful Princess Who Solves Everything, but what they ended up doing was creating a well-intentioned female authority figure and then beating us about the head with how powerless and useless she ultimately was except as a symbol to the main (male) character. This wouldn't have been so bad if they hadn't also shunted Shirin out of power when she would have made an excellent political leader.
As for the relationship between Setsuna and Marina, I have trouble reading it as something that could develop into a conventional romance under any circumstances. This is hypocritical of me to say as a Lockon/Tieria shipper, of course, but them's the breaks. I just can't read Setsuna and Marina as wanting each other in that way. I don't know if that's the intention, or if it was a writing fumble. In the end, their relationship reads as platonic to me because it's Platonic: they're symbols to each other as much as they are people, and that's all they need from each other. There's a lot of metaphor and dream and thinking soulfully of each other, but not much interpersonal connection as people.
By contrast, even though I think of Setsuna as asexual and there's little real evidence for it in canon, I ship him with Feldt because on the rare times they do get screen time together, they're very awkward and real and human around each other. They show feelings beyond a vague yearning for ideals. I can see Setsuna forming a family with Feldt, based around Celestial Being, their shared connection with Tieria, and their shared memories of Lockon. It's nothing that I want to see happen in canon, but it's something that makes me smile in fic.
Whereas Setsuna/Marina seems kind of complete as a symbolic, spiritual thing without any visceral or physical side to it. I don't know.
By way of hashing out my feelings on Setsuna/Marina and how they appear in the new comic, I wrote something that will probably get posted on 31_days for June 19, "more vital than sane." I don't know how I feel about it. We'll see.