Alanna Masterson as Domino (Marvel Comics)

Domino was originally created by a government super solider program but with her power deemed useless she was abandoned and eventually become one of the world's top mercenaries using her power of probability control to make herself exponentially more dangerous than she already was. In her early life Domino was bounced around working for carrying government agencies before becoming a member of the mutant group X-Force. Even though Marvel isn't itself making the x-men franchise i think Domino's backstory could be edited easily enough to allow her to appear in the MCU my idea in this pick would be for her to appear in The Defender's franchise. An assassin with superhuman luck could easily have a place there and with more Nuke coming hopefully in The Defenders we'll be getting new and different super solider programs into the MCU. 

Alanna Masterson is currently playing Tara on The Walking Dead, which is sadly sailing face first into the ground, so Alanna needs to find herself work that reflects her talent more. She's clearly proven herself to be a tough action star who's good with guns and knives and is physically big enough at 5'8 to play someone who was created to be a super solider. With the right stunt coordinator i think she would be able to pull of Doimino's fighting skills easily.