Nate can get a big payday on a 3rd fight with McGregor which will happen when he loses the belt to Ferguson or Khabib. The window is closing on Nick, maybe he can sell wolf tickets with a GSP fight. But if I'm GSP, I would be looking for big money fights that come with a belt vs. Bisping, Woodley or Conor. Beat Bisping at 185, vacate and go to 155, beat Conor and then go back to WW for his old 170 strap. I think he beats Bisping, but would not want or be able to defend (Romero, Souza, Rockhold, Weidman, etc.) as he is simply too small for MW. GSP can beat Conor if he can get to 155. Woodley, Wonderboy are no sure thing for GSP at 170. Both great fighters in their prime.
I think Nick should fight Lawler which would sell, be entertaining and a great story line rematch. I think Lawler takes the fight whereas GSP accepting is less than 50/50. Lawler will stay in the pocket with Nick, little or no wrestling most likely. This could be main event or co-main event.