If the plan is for Becky and Charlotte to be involved with Ronda at Mania, I don't see the point in having Lynch regain the Smackdown women's title.
Not sure how they're gonna do it tho, maybe Charlotte could interfere in favor of Asuka or Becky loses clean and covers it up by winning the Rumble. One way or another, from both a logical and personal standpoint, I'd go with Asuka. She's a great champion for when Becky and Charlotte (possibly) move over to Raw.
I just hope Becky and Asuka do well with the match itself. They never faced each other in a singles match before