The strawweight division has opened up, I think Rose or Joanna could win a decision against Weili...I'm not sold on Tatiana Suarez yet though, she definitely has the wrestling but the striking and cardio to go 5 rounds is in question.
Wouldn't be surprised if they book Waterson next, maybe in China again since she is of Asian descent too.
Some problems with your theory.
1. Waterson is booked to fight Joanna in October in Tampa.
2. Suarez is most likely getting the next title shot.
3. They won't be back in China for probably close to a year.
4. Dana said Weili's next fight will be in the USA.
Waterson's side already made it clear that she wouldn't fight outside of the US. Miss I'm Too Good to Fight In A Different Country can stay her butt at home. Being part Thai would do nothing for Chinese fans regardless.
She'd get rocked by Weili anyways. Anyone who has actually followed Weili up to this point in her career would not be betting against her.
Only idiots like Brendan Schaub would say "she'll get steamrolled by Andrade"
Well, it worked out for Waterson. She got a main event fight, in the USA, against a much bigger name, and as good as Joanna is, she doesn't hit nearly as hard as Weili.
Couldn't believe Schaub's take on that fight. So obvious he had never see Weili fight. He phones it in quite a bit as a MMA commentator, but that one was bad. Picking Andrade is one thing, but steamrolling through Weili?
Business/marketing was a big part of it but as others have said, other contenders weren't available either. As for Waterson, the rumour is that they wanted Zhang vs. Waterson as the main event for this card with the winner possibly getting the next shot. Apparently Waterson turned down the fight because she thought she deserved a bigger fight or title shot, which upset the UFC (Dana) so they gave Zhang the title shot instead. At the press conference when he said, "no one wanted to fight Zhang", that appeared to be him throwing some shade at Waterson for turning down the fight.
Well, he must not be too upset. A main event against Joanna in the USA is way better than going to China to fight Weili.