Man oh man there would be nothing i like more than to see more of Black Widow, that means that we get to see more of Scarlett Johansson and her awesome portrayal of Black Widow. They have a lot of storylines to fall back on for Black Widow. It could even mention other Marvel characters she has interacted with over the course of her career as a master spy.
Black Widow and Elektra:
Black Widow and Daredevil:
One storyline they can go with live action is when Black Widow went toe to toe with Elektra and Daredevil, i would love to see a fight between them and a better representation for Daredevil and Elektra also. Scarlett is completely on board with a movie about Black Widow in fact she embraces it. With enough fan support and a solid story i don't see why this shouldn't get a live action movie especially since Black Widow in the comics did some solo work after the Avengers so why not capitalize on that.