Hm, find out how the other ones do it? Seems like it would be a lot easier to do for a single pairing remix than multi-fandom. I know that Remix Redux doesn't allow you to specifiy pairings, only fandoms. It could be a random match up instead of trying to match people up to specifics. It's more of a challenge maybe for the writer, but at least you know you'll have a body of work to choose from that is R/S. And there has to be a pool of at least five fics to choose from or something like that.

I wonder how many people in the R/S writing pool would sign up, though.

I have no experience managing this sort of thing, but I would be willing to help. ;)