I think Kos "plays the heel" better than Fitch and is arguably the more recognizable mainstream name and could hype a fight with Diaz to epic grudge match proportions, since nowadays it feels as though there is more interest in "selling the fight" than rankings....
I think Fitch would be the superior challenger, but I don't know if ZUFFA wants to risk the money of GSP/Diaz by having a stud grappler like Fitch derailing him, similar to when SF didn't matchup Fedor and Overeem off the bat or at least in the first round of the GP and then lost out on the incredible main event, due to Fedor dropping fights to Werdum and Bigfoot....
I think they book Fitch/Maia and Diaz/Kos and if Hendricks loses to Kampmann, they book Hendricks/Ellenberger. Once Condit loses to GSP, they book him against the winner of MacDonald/Penn.
MY MMA RANKINGS
HW Velasquez Cigano Werdum Cormier Bigfoot Barnett Mir Browne
LHW Jones Machida Evans Hendo Davis Goose Teixeira Shogun Mousasi Bader
MW ASilva Rockhold Belfort Weidman Jacare Okami Kennedy Consta Belcher Boetsch
WW GSP Hendricks Condit MacDonald Diaz Maia Fitch Kampmann Ellenberger Pyle
LW Bendo Alvarez Maynard Melendez Thomson J.Miller Diaz Pettis Chandler Grant dos Anjos
FW Aldo Mendes Curran Lamas Frankie Zombie
BW Cruz Barao Fernandes Faber Moraes