The famed shonen series JoJo's Bizarre Adventure features not one, but a handful of protagonists, starting with the brave and noble gentleman Jonathan Joestar, then the wily and crafty Joseph Joestar, and lastly, the stoic but loyal Jotaro Kujo (who defeated DIO for good). By the events of Golden Wind, Giorno Giovanna was the hero, but it could have just as easily been Bruno Bucciarati.
Bruno Bucciarati had already formed his own squad of vigilante heroes by the time Giorno was stepping onto the stage, and Bucciarati earned a place in the heart of the entire JoJo fandom. It's easy, therefore, to conceive of him having his own spinoff series.
Bucciarati Has The Makings Of A Hero
Bruno Bucciarati has all the makings of a main protagonist, and not just from a shonen anime perspective. To begin with, he is a proactive character, one who refuses to accept defeat. If there is injustice in the world, Bucciarati is quick to take bold and decisive action, and he doesn't need much of a push, either. Like the other JoJo heroes, Bucciarati has a can-do attitude that moves the plot forward, and a golden rule of fiction is that the protagonist must not be passive.
Things must happen because of the character, not just to them. For example, Bucciarati struck back against drug-dealing mobsters when he was a boy, and saved his father's life at knifepoint. It was a gruesome scene, but it did establish Bucciarati as a doer, and not just as a spectator. Later, he resolved to take down the corrupt crime boss Diavolo himself and formed an entire squad to get the job done all on his own.
Bucciarati could be the hero of his own spinoff series because he has the same courage, grit, creativity and resourcefulness of the other JoJo heroes, something that the series is known for. Some shonen heroes simply power their way through the opposition, but in this series, a quick and crafty mind is the key to victory, and Joseph and Giorno, in particular, are high-IQ fighters. The same is true of Bucciarati. More than once, Bucciarati turned around steep odds in battle with his zipper-making Stand and Sticky Fingers, and he never had to "cheat" his way to victory. If Bucciarati had his own spinoff prequel series, he would face the forces of evil and triumph in the true Joestar way.
A Spinoff Could Reveal More Of What Came Before
Through a series of flashbacks, viewers found out how Bucciarati recruited the other members of his team, such as the lone gunman Guido Mista, the disgraced ex-cop Leone Abbacchio, and the hotheaded Fugo and Narancia Ghirga after that. But these were just flashbacks with heavy narration, while a Bucciarati prequel spinoff would be a chance to see these heartfelt stories fleshed out in greater detail (and there would be no need for an info-dumping narrator, either).
The life experiences of Bucciarati and his fellows were violent, gritty, tragic and exciting, and of course, that would make for good fiction in a prequel series. Viewers could see more of Leone Abbachio's failed career as a police officer and Bucciarati's development as a master Stand user, all at a leisurely pace that gives the story a chance to show itself naturally.
Such a prequel series could give a lot more context to the main story of Golden Wind, and it wouldn't feel like a needless, tacked-on sequel since it's covering material that is central to the story of Golden Wind. That's an advantage of prequels like this; they don't have a "more for the sake of more" feel that some sequels end up having. In a lengthy OVA episode, viewers could get the full (and vital) story of how Bucciarati and his squad came to be. With one spinoff already on the way, why not another?