Not sure if I agree with your "percentages", but the smartest thing the UFC could do is convince BJ to fight at LW, and give him 2-3 middle of the road fights, hope he returns to his former self, and market a title fight (although he'd likely get stomped on).
If they got him to return to lightweight, and give him somebody like Pettis, and then a top 10 guy like dos anjos, cerrone or alvarez and he wins, they could possibly sell a LW title fight. Otherwise I have no idea what BJ is doing, other then collecting paychecks and getting thrashed in a division he shouldn't be in. I'd rather see him gatekeep in the division where he was once a champion, not get wrecked in a division that he will never accomplish anything in.
My percentages are based on the divisions being mid-top heavy, 50% of the current WWs are not really that good (comparatively), BJ is better than average at that weight. I believe he is still pretty good at LW, maybe just outside the top 10 if that when he is at his best (15-20 range at worst).....