My preferred pairing is Jack/Ianto, but I'll read other pairings if I like the author. I just wrote my very first pairing that was not Jack/Ianto (Tosh/Suzie), though I did throw some Jack/Ianto in there.

I actually don't like to read non-canon pairings of characters that are paired w/ others in canon. What I mean is, I don't read Ianto/Owen b/c I see no basis for it, likewise Gwen/Tosh. They feel OOC to me. That being said, I'm willing to try it out if I trust the author (like your Tosh/Rhys and neifile's Jack/Ianto/Owen), and if other people want to write it, by all means, have at it.