Well, on the question of whether an OC (specifically, my watcher Richard Philips) should be involved in a romance with a canon character (specifically, the kinda/sorta resurrected post-Chosen lesbian ghost witch Tara), the vote is:
"Sure, it's your story" (I'm wondering if I worded that fairly): 13, or 68.4%
"No way, he's a Mary Sue" (which is true): 3, or 15.8%
"a little flirtation would be fun" (also true): 3, or 15.8%
http://www.livejournal.com/poll/?id=922420 Now, there's a secret statistic, one I didn't mention in my post. Granted, I was curious about attitudes toward Mary Sue's in general. But I've gone to great lengths to make Richard well rounded, and over the course of a dozen stories I honestly feel he's evolved into a separate person, no longer a Mary Sue. So I'm happy to announce that as far as I know, everyone who's actually read the story voted to continue some level of the relationship between him and Tara.
I usually hate Mary Sue characters, myself. The cliche's are often true, and if I'd encountered this poll without reading the story, I would have voted "No way!" So I believe those who voted without reading have a perfectly valid and probably wise opinion. However, the fact that those who did read were okay with the idea makes me think I did a good job creating Richard as a "real" person. Does this make sense? It's 6:30 in the morning.
Just the same, I haven't decided if I'm going to involve them in a romance. There are issues -- for instance, he's much older, and Tara's dead. But my stories are all in the same continuity, so they'll continue to encounter each other from time to time ... maybe a bit of a flirtation might be fun. Opinions?