A character who originally started out life as a Batman rip-off, Arrowcave and all, Oliver Queen has since blossomed into one of DC's most unique and compelling vigilantes. He has the iconic beard, the partnership with Black Canary and a veritable troff of trick-arrows to choose for any occasion - what's not to love?
With his existence in the Arkhamverse having been confirmed in an easter egg from Arkham Origins, there's also precedent for the character to make an appearance. Throw in the added prospect of dual-play with Canary and other supporting cast members, along with the added threat of the bow, and you have the premise for a truly compelling - albeit unexpected - entry in the Arkham saga.
The character's overdue a title of his own, having only appeared in Justice League Heroes and both Injustice Games. It makes an Arrow title something of a priority, whether it be made as an origin story on the island in the vein of Tomb Raider, or during the character's golden years during the Bronze Age.
More important, perhaps, would be divesting from the ersatz version of Batman displayed in The CW's Arrow - a prospect fans of Oliver Queen would be sure to eat up instantly.