One great fanfic could be 'The Unexpected Bond'. It beautifully captures the chemistry between Anthony Mackie and Sebastian Stan. The story delves into their characters' deeper emotions and relationships in a really engaging way.
Fanfiction.net is also a good place. There are many dedicated writers who post their works about these two actors there. Just be aware that the quality can vary, so you might need to do some sifting through to find the really good ones.
As of now, I haven't heard anything about Anthony Mackie specifically requesting a Black Widow love story. The Marvel Cinematic Universe has a complex web of storylines that are designed to fit into the overall narrative arc. A love story between his character and Black Widow would be a significant departure from what has been established so far, and it would likely require a lot of groundwork in terms of character development and backstory. Moreover, with Black Widow's story already having its own arc, including her sacrifice, it's not clear how such a love story could be integrated without undermining the existing narrative.
As far as is publicly known, Anthony Mackie hasn't had a highly publicized love story in the way some other actors have. He might be in a relationship or have been in the past, but he doesn't seem to flaunt his romantic involvements. His focus seems to be on his work in Hollywood, starring in movies like the Marvel series. So, unfortunately, there isn't a well - known love story that can be easily told about him at the moment.
One possible reason could be to expand the emotional range of the Black Widow character. A love story would allow her to be more than just a tough spy. It could also be a way to connect her story more closely with other characters in the MCU. Maybe Mackie thought it would make for a more engaging storyline for fans, as love stories are often popular elements in movies. Another aspect could be to explore different themes such as sacrifice and loyalty in the context of a romantic relationship for Black Widow, which would be a new and interesting take on her character.
If he requested it, Marvel might consider it but it would be very challenging to implement. They would have to rewrite parts of the existing storylines to make it believable. It could also change the perception of Black Widow's character, as she has a very distinct identity in the MCU already.
Well, it could be a very interesting concept. Maybe it would show a side of Black Widow that we haven't fully explored in the context of a relationship. Anthony Mackie's character could bring out a different aspect of her personality. However, in the MCU, Black Widow has her own tragic backstory which might make a love story quite complex.