I think it's clearly the best fight to make. Champion vs. Champion; Bisping will make weight and had a camp recently so will be pretty much in fight shape; Bisping just beat Rockhold so there is storyline because Rockhold and DC are boys; Bisping is the ultimate underdog and is a roll right now; it doesn't hurt Bisping's stock at MW if he loses; the title can still be on the line...
Or DC vs. a random HW in a non-title match... Also, there are no good HWs ready to go unless they scrap another fight.
Bisping, the guy who was never destined to be a UFC champion, would have a shot at becoming the first ever simultaneous two-division champion.