I'm very old HL fan and read enormous amount of fanfiction, old and new. And I can see changes in this. I'd say total tendency there - it's bring Methos on foreground (which wasn't in canon exactly). Of cause it thanks to charm of Peter Wingfield (whom we become well-known after show as he is really amazing person).
Actually it's not bad tendency. It brings new colors to Methos personage and to fictions on the whole. But don't forget about canon!!!
For me it's very sad that more and more writers write Duncan as limited judgemental bastard etc. If it was true, I don't think Methos would have the desire to come into his orbit and to befriend him.
*g* About pairing.))
Again. If we remember the canon there...
More edible and plausible pair would be M/D of cause (but not necessary). All we can see chemistry between them in the show (which gives carte blanche to any fantasy).
M/J for me is improbable. I can't see this in the show, where they wasn't even closest friends. Again, all this subject brought in much later when we know about friendship between PW and JB.
M/R ... It's ridiculous! What common things could be between ROG with so many layers and youngster as simple as bald knee?? Again in the show Methos had no slightest interest to Richie.
M/Amanda ... hm hm hm...))) But maybe they have chemistry more like two devilish minds then lovers? There plenty room without sex playing for.
M/Rebecca. Don't think so. There wasn't slightest hint they even knew each other. So what the point? Or had Methos necessary conscription to have affair to any old immortal on the planet?
If we want more diversity, I think there are many opportunities to play with original characters. There any fantasy we capable of.
Just my point of view. :))