Ah, yeah, that makes sense. I'm kind of the same, though for example if it went AU from just before Ron and Hermione got together and she was all "I see you as a brother" I'd think "But...we know that at that point in canon she didn't!"

Yes, some pairings are more supported by canon than others, and this is not necessarily correlated to how much I like them.

Hmm...yes, I think we're similar here. I definitely have pairs I ship JUST as friends, and if I ship two people romantically and their relationship hasn't had much attention in canon I really enjoy gen fic exploring and building upon their relationship, even if part of me wishes it was shipper :)