Cincinnati has a history in the NBA. Look at the picture and look up the Royals (now known as the Sacramento Kings).
If the Celtics were to do stints in Irish populated places like Pittsburgh, St. Louis, Kansas City and Cincinnati, or any mix thereof, it would increase Celtics Nation. The aforementioned are some of the most populated Celtic places not represented in NBA America.
With a concept like this, any market brand could increase and be encroached upon. Think the LA Lakers of Buffalo. The West Coast Clippers part-time in Seattle or even Honolulu. The Jets aren't named the New Jersey Jets or the New York Jets of Jersey. The California Angels became the Los Angeles Angels of Anaheim. Would they ever split some home game time as the Los Angeles Angels of Las Vegas? It's a thought. It's an option. If the Toronto-NYC Jets flew at the Bills every once in awhile, would that not become a heated rivalry?
So many options: Cleveland Cavs of Cinci. Indiana Pacers of Cincinnati ?