If we're only getting one more male (1m/1f like Injustice) I agree, I'd want Fujiin. Personally though I'd love if they did Fujin, Li Mei, and then the three story NPCs. Not holding my breath, but I think that'd be perfect.
As I already mentioned, I would very much like to see an all-female "Femme Fatale" DLC.
Given that MK is targeted at a (mainly North American) "comic book" audience (in lack of a better description), and not a "anime/manga" type audience, such a DLC is probably not going to happen and male, muscle-bound brutes will continue to be the norm.
With this in mind, I resigned to one -- or two, at best -- future female DLC characters. But who would I like to see (not that anyone cares)?
As much as I love
Sindel,
Skarlet (and to a lesser extend
Jade), they are still in a semi-current MK game (MK9)...
Thus, my 1st choices for a comeback as DLC would be
Sareena and/or
Nitara.
2nd choices would be
Li Mei and
Ashrah. Although, if they make Li Mei a playable MKX character, I sincerely hope they improve her design and make her look more feminine and pretty (to me, she looks quite manly in MKX story mode), i.e. make her look more like Xiaoyu from Tekken (and less like Elektra from 80's comics).
My favorite male character for a comeback would be Stryker, Sektor, Cyrax, and Baraka.