Craig - Adele - This one could work. Both have quite a lot of personality and it could make great chemistry onscreen.
Janet - Ellie Goulding - only because I doubt Florence would appear on XF yet that would be much more entertaining than Janet and Goulding. Otherwise she may get this Ed Sheeran character I keep hearing about.
Sophie - In an ideal world- she would have been marketed to us completely differently and Amy Winehouse would have been her partner. Alternately, Bruno Mars.
Marcus - another toughie, Jason Derulo - They could do Solo since Marcus shows an aptitude for dancing.
Rhythmix - Jessie J - they could sing Price Tag or Do It Like a Dude especially since she was Tulisa's judging partner.
Johnny - ideal Scissor Sisters but as that bird has flown (what happened to them?) obviously Kylie although Beth Ditto and Johnny Standing in the way of Control would be lovely.
Kitty and Gaga - the country song she has out now. I don't think LG would do it though.
Frankie and Robbie - with what song is a mystery to me. Robbie is the only one who would tolerate Frankie's lack of talent and mainly because Gary says please.
The Risk and Tinie Tempah - sure they could work something out. Please not The Wanted who seem to live at XF along with Prof Green.
Misha B - Nicki Minaj (I think Missy has been ill for a long time) or Estelle doing American Boy