Digging the discussion and ideas going on in here!
Using a few of the ideas in here, these are a few arcs I think could work really well:
Arc 1- Agent 37. Dick works a series of missions to help out his old pal Tony the Tiger, head of Spyral. These missions are all in places where the Justice League, or any hero, operating openly would cause an international incident (like perhaps Biyalia from Young Justice). Dick frees trafficked metahumans, prevents hostile coups led by disguised supervillains, intercepts alien weapons shipments on their way to hostile regimes. This arc, featuring Tiger, the Skull Girls, and other Grayson favorites, reaches its climax when Dick discovers that Tiger has lead Spyral back to its nefarious ways.
Arc 2- Dick vs Spyral. This arc opens with a pitched battle at St Hadrian's. Dick has called in favors from the Titans and other heroes. Tiger was prepared for this assault, as he expected Nightwing to think like a hero. Dick, however, is thinking like a spy. Using the conflict as a distraction, Dick sneaks into Hadrian's (with the help of the Skull Girls perhaps), and steals vital intel on Spyral agents names and assignments. With this intel, Dick uses Batman Inc agents to fight Spyral from the shadows. This arc reaches it climax as Dick finally confronts Tiger and wrestles control of Spyral away from him.
Throughout this arc, Dick has been preparing for the future. He has pitched his idea to Bruce and Lucias Fox to "diversify" Wayne Enterprises holdings by building the premier high rise casino in the heart of Bludhaven. By the end of arc two, Haly's Casino, with steel and glass architecture reminiscent of a three ring circus tent, has been completed and is open for business. This now functions as Dicks day job ("owner and operater"), home (penthouse suite like during his Batman days), Nightwing's lair, and Batman Inc/Spyral HQ.
Arc 3- Dick gets a sidekick. There are many ways to go here, from bringing in Damian, some unused but preexisting character, or creating a new character specifically for the book. Giving him a protege, does a few things. First, it gives him a partner to talk to while he's in bludhaven, the importance of which cannot be understated. It also shows his progression as a hero, starting as a sidekick and coming full circle to training one himself. Finally, it would give him an increased pretense in Bludhaven, and someone to fight street thugs while he is away on spyral business.
By the end of these three arcs, a new a status quo has been established. Dick is the director of a combined Spyral/Batman Inc. He lives in Haly's Casino. He defends Bludhaven as Nightwing (wearing a Young Justice inspired bird symbol costume) and gets hands on in the field as Spyral's director (wearing the Chuck Dixon era inspired chevron/finger stripes on his spy gear).
This status quo opens the doors to important supporting character. I'd envision him having an important assistant director/secretary type character to deliver him briefings from agents in the field and through whom to deliver new assignments (more interesting to have this be a discussion than him opening emails). (I really would want Alfred for this role, but that may not work given his need to primarily be with Bruce.) Obviously his protege would be a huge supporting character. He could be a "home base" for Haly's circus when they aren't on tour.