I can already sense a lot of negative comments. But deeply thinking about this, you gotta admit it would be perfect.
You can't blame her for Catwoman flopping. The character just doesn't work in a solo film. Halle Berry also was an X-Men, Storm. I never really liked her as Storm. To me she was just hired for the star-power. Storm's history is traced back to Africa, so they chould have at least hired a full black actress.
Anyway, this would be perfect. Especially if she is featured in The Avengers. If not, imagine her in a SHIELD movie. Samuel L. Jackson, Scarlett Johansson, Halle Berry, and Bradley Cooper(My fan favorite Hawkeye, but I'm not gonna get into that right now).
And of course the race issue. Some may be saying, they already darkened Nick Fury, now Maria Hill. I think changing character's race is sometimes needed. Not just black, but any race. Adding a different race behind a character can really add more dimension. What other actress do you know could this job without being a reflection of Scarlett Johansson's Black Widow. Plus she actually looks like her.
Halle has worked with Samuel L. Jackson numerous times, just as much as Scarlett Johansson has. So you can guarantee chemistry. I'd like to imagine Nick Fury and Maria Hill's relationship similar to Tony & Pepper.
Halle has also worked with our Tony Stark, Robert Downey Jr. in Gothika. Though their relationship in that film would be absolutely nothing like in the Marvel Universe, they are good with each other is the point of mention.
AND what other actress can you imagine Directing SHIELD at some point, and has as much star power. Plus you gotta love how Halle would be in Maria's Tight suit.