I can give you something.
Like Batman, Oliver Queen and Dinah Laurel Lance are seasoned crime fighters too, since all three of them know each other and have had team ups together in the past.
Yeah, it's better to have most of these characters already established.
If I had to envision Green Arrow for a movie, I would make some changes from what we currently see in Arrow. Just like Bruce is to be influenced by Zorro in BvS, Oliver had a great love for Robin Hood. He would be inspired by the tales and movies of seeing his outlaw idol fighting against the corruption of the higher powers, their greed and hypocrisy, taking their money and giving it to the most needy - all the while, doing it, with a weapon that Oliver became obsessed by; the bow and arrow.
Soon enough, Oliver had purchased for him, a bow and arrow, and a tutor to teach.
Oliver's parents would have been killed when he was younger on a safari trip in Africa. He could have saved them if he had killed the Lioness that was on her hunt, but failed to do so, as his bravery, courage, and archery skills, simply weren't up to the task. Oliver would be raised in the care of his uncle, a man who did not share the passion and the charitable traits of the boy's parents. Often manipulative and corrupting after taking over Queen Industries. His ideals, hopes and beliefs dying before him, and blaming himself for his parents' deaths, coming to lose his admiration for Robin Hood, and his love of archery, Oliver soon changed from the light hearted and optimistic boy, into an unruly, depressive, womanising, gambling, alcoholic, drug dependent young man.
Then, once he becomes stranded on the island, he goes through that dangerous metamorphosis and rediscovery of self. Now this is the psychological aspect that I've been exploring - pure isolation. Is it a positive thing to experience, or negative? In Oliver's case, it's definitely positive AND negative. The initial fear of being stranded until you die, it's pretty bad. But just imagine you're a guy like Oliver; completely self-destructive and placed within an environment where there is potentially zero hope of surviving past the first week. The survival instinct will kick in at some point, but Oliver is a young man who has literally given up on life anyway. Coping with his anger, guilt and self-hatred, the lack of hope for a brighter future, he'd be surviving based just on natural, raw instinct. Combined with that psychology, other factors would be sure to kick in, especially his slowly decreasing humanity. Decreasing, but never lost. The lack of communication and interaction with other people, preserving his own self character on a day to day basis, will revert him to a more primal form. Eventually, in between and after his new animalstic nature, his mind will begin to wonder and present him with questions on who he once was and how he found himself in his situation. Meditating will help Oliver reflect on all his life, focusing mainly on the positives, creating a hope that he may put a right to all the negatives. Soon enough, this hope, becomes his main reason of survival. All of this journey of rediscovery gets put to the test when Oliver discovers a drug ring brought to the island. Seeking to only escape by boat at first, his new nature, combined with everything else he has constantly thought about on the island, kicks into play...He hunts and kills the criminals, using the make shift bow and arrow he was forced to create in order to survive, drives the boat filled with drugs back to the mainland, delivering them to the authorities, and steals the cases filled with drug money, leaving it a hospital as a donation.
It does sound pretty dark to say he kills the criminals, but I believe it to be fitting, considering his isolation on the island, combined with his other psychology factors
To make him light wouldn't be fitting with the DCFU. If anything, I'd make him darker than what he is in Arrow. In that show, he has the conflict over killing, or did. Whereas here, he doesn't. His journey and time on the island gives him the 50-50 balance of light and dark, human and animal, hero and outlaw.