Since he didn't get Frankie, the only fighter that would make sense is Jeremy Stephens, which would be a fun fight. I would say a rematch with Charles Oliveira but I doubt he would get cleared by December.
The other option would be wait out the loser of Edgar/Mendes (or Mendes if he wins for a title eliminator), but that's probably going to be 6 months minimum and I'm sure he'll want to fight before that.
Ideal scenario is a match-up with Jeremy Stephens and serve as a sub for Edgar-Mendes in the case that one of them gets injured or Aldo pulls out again and Edgar takes his place.
Thoughts?
I think Stephens 
Since they've already made Edgar/Mendes (great fight) it's gotta be Stephens. Assuming he can make weight. And assuming they don't want to do an Oliveria rematch because of the flukey ending.