Arrow started a universe that now includes The Flash and [DC's Legends of Tomorrow](tag:2937021). But the show is soon going to reach its original planned ending date. With that in mind, I believe after the end of the five years, the show should either take a new direction or have another show take over its time slot. And I think the best idea would be to base the show around Arsenal.
Whether or not it gets a new name is irrelevant. He could easily go to Blüdhaven to fight crime there and run into heroes and villains not yet in the Arrowverse. Here are 5 characters that would be great for the show:
Cheshire is a villain in the DC comics universe. She doesn't have any superpowers, but is one of the best martial artists in the world. She will often tip her fingernails with poison.
I chose Cheshire because of her relationship with Roy Harper, and because she fits well in the Arrow-verse. She is romantically involved with Roy and eventually has a child with him. This would make an interesting dynamic similar to Batman and Catwoman.
Nightwing is the first Robin, Dick Grayson. After outgrowing the Robin persona, he strikes out on his own as Nightwing. Blüdhaven was actually created to be a city for him to fight crime in, just like Batman has Gotham.
I choose him for a couple of reasons. First, he belongs in Blüdhaven. It would be like going to Metropolis and not running into Superman. Second, he would fit well in the Arrow-verse, without needing Batman to appear or even be mentioned by name. And third, the dynamic between two heroes who left their respective mentors to strike out on their own could be awesome if done correctly.
3. Killer Croc
Killer Croc is a villain who was born with a genetic disorder that made him more beast than man. He was bullied constantly as a kid, and grew to hate humanity. But he has also been shown as a sympathetic character in some stories.
I choose him because of his history with both Roy Harper and Nightwing. Being primarily a Batman villain, Dick Grayson has had to fight him more than a couple times. He also has an interesting relationship with Roy. He spares Roy's life when he tries to commit suicide, telling him that "it isn't his time." Roy later is shown in a bar, and implies that he isn't drinking because Croc wouldn't approve.
I feel like Croc could become the Captain Cold of this show. Roy's arrows and fighting techniques would probably be ineffective against him due to his size, strength, and tough scales. So Roy would have to attempt to steer him away and slow him down, but would have a hard time stopping him outright. So even if his plot is foiled, he can still easily escape and fight another day.
Tarantula is a vigilante often associated with Nightwing and Blüdhaven. Like the Punisher, she uses extreme tactics to pursue criminals and comes into conflict with heroes.
I choose her because of her relationship with Nightwing and Blüdhaven, and because she seems like she would fit right into Arrow.
Blockbuster is a villain who was one of the largest crime lords in Blüdhaven. He was given experimental steroids to save his life, but now has super strength. Although he isn't very smart, he tries to compensate by becoming as strong as he can.
I chose him because of his history with Blüdhaven, Tarantula, and Nightwing. He also would be a good villain for Roy Harper, who has already had to fight Brick.