Well getting 4 players together at the same time will definitely be the major problem to solve. On the 81Doju Chu-Shogi server (AFAIK the only one in the world where you can play live Chu Shogi, a game that has tens of thousands of players) there are typically zero people to be found.
Do you already have a design in mind for how people could negociate a time to play a game, when they would never be present on the server at the same time spontaneously?