1) As Scarlett Johansson rightly stated, Black Widow’s history is rich, and steeped with great stories to tell. As a spy, she has been involved in so many organisations, and this has been touched on by the MCU, which uses her as a bridge to connect HYDRA and the Red Programme, The Winter Soldier and SHIELD. Exploring her past in a more comprehensive manner would have the advantage of revealing her associations to each, as well as weaving a complex web of relations.
2) Natasha Romanoff is a Russian woman. To have her star as a protagonist would be a huge leap for Marvel, as characters of non-American ethnicity, when featured, are generally played as villains or thugs, rather than with heroic story arcs. This is superbly illustrated by the fact that the woman that Marvel has picked up to title the first solo superheroine film is Carol Danvers, a white American woman with a military background, despite Natasha’s pre-existence as a popular MCU character.
3) The Black Widow is very popular (and the lone Marvel superheroine). She has an avid and dedicated following, who would be more than willing to watch and applaud a solo film, as seen from demonstrations, tweets and general comments made since Natasha Romanoff first appeared on the big screen. Furthermore, there is no disagreement from higher levels such as Kevin Feige. It would be a very easy sell.
4) There are already fanmade title sequences and trailers of the film! Beautifully made, one has tricked many an unsuspecting Marvel fan that a Black Widow film was on the table. In fact, given the quality of the trailer, if the film was made, it might outstrip the rest of Marvel’s creations so far. Additionally, there’s no shortage of actor, writer and director enthusiasm – a treatment of the film was written back in 2010, and many celebrities have been quoted as saying that they’d be on board with the enterprise.
5) If a movie were to be made, it would give audiences the added pleasure of potentially delving into Hawkeye and Bucky Barnes’ histories as well, uncovering more backstory and spy shenanigans.
Reasons 6-500) Natasha Romanoff is one badass lady, and on top of that, she is a chameleon. She evolves, constantly. Wouldn’t it be awesome to watch those metamorphoses on screen? (the answer is a resounding YES).