Honestly, I had kinda hoped that the Tyrion x Sansa marriage would work out, since they're two of my favorite characters; so I'd be totally in for that. I'm not sure how we would work it in to the story though. Maybe that's just because I haven't finished the series. Do you have any ideas?
During season one could work. The equalist threat could make things interesting. Season two could also work, but there aren't as many options. Alternatively, we could do Tenzin x Lin when they were going out, pre-series. Though it will be doomed to fail....
Personally, I try to mirror the character as close to the author as possible. So, with that said, I don't think that Snape x Hermione would work before she leaves school (AU in terms of Snape's death). As for Lupin, again, it would have to be AU, in terms of Tonks and death, and it would have to be after school for Hermione. Another thing I've seen done though, is a marriage law. Where Snape x Hermione or Lupin x Hermione are paired by Dumbledore to prevent a marriage to a Death Eater. I hope I answered what you're getting at?