The way posting is done irks me, too. It's outdated as a method and is really counter my writing style of tweaking until the clock runs out. I also really dislike having the comments on the story get effectively lost since I can't see them unless I go to the comm and look, which also runs the real risk of there being comments I never know about.

I think your other concern is unfounded, though. Yes, a lot of the fans are ROG fans, but I don't think anyone is exclusively. There are at least two people already signed up who'd delight in your ability to write a historical story about Duncan, and at least two others who'd appreciate your willingness to write Richie or one of the other underwritten characters. Amand-r is as careful about matches as you are, so she'd try to make sure you got someone you'd work well with, both directions. Obviously, perfection is not guaranteed, but the participants seem to be a pretty easy-going lot. Heck, last year I had to ODAO my match in a big way and I still got a nice comment.

I'd really encourage you to give the exchange a shot. Not that my reasons are unselfish, or anything :)

(Some of us obsessively rewatch the middle two seasons. There's as much spread in HL fandom as there is in FK.)