Should get called up: Nikki Cross
As evidenced by her recent "I know a secret" angle, Cross has tons of charisma and a great presence. The Scottish Psychopath has been most impressive in NXT. First, there was her vicious feud with Asuka, which culminated in a brutal, first ever Last Woman Standing match that saw Cross put through the announce table. She was also the only woman with enough presence and panache to hang with the loonies in Sanity and was a premier member of the group.
However, when that faction was called up to the main roster, she remained on NXT.
Her look, character, and outrageous brawling style are all unique in the WWE's women's division. With all respect to Ronda Rousey, Cross is the wrestler who most reminds us of Rowdy Roddy Piper at present.
Nikki Cross has been ready for the main roster for at least a year. Time to give her that call, Vince!