#4 Nikki Cross (SmackDown)
Technically Nikki Cross has already had a match on SmackDown against former Women's Champion Becky Lynch. Her move to the blue brand also means a reunion with Sanity, and the stable really needs their unstable sister to have an edge over others.
On her run in the women's division, SmackDown would prove to be a much better place for her title aspirations. Becky Lynch and Charlotte would probably move to RAW, for the title. Even if Charlotte stays to compete against Asuka, Nikki Cross could be a future contender, with all her experience in NXT.
Overall, the RAW women's division is packed with female superstars who could be in the title picture, which gives SmackDown a chance to insert new blood like Nikki Cross in the title picture.
She could reignite her feud with Asuka, but this time for the SmackDown Women's Championship.