Don't forget political considerations. If flying from Taiwan and Macau isn't available, don't think about using Shenzhen or Guangzou unless you are really stiffed. Landing in the Peoples Republic of China and being asked "where did you take off from", answering "The Republic of China" won't be a very good answer. Expect a long stay and lots of questions.
There is also Zuhai (just south of Macau) to consider, and don't forget Manila or other Phillippine airfields.
Also, if aircraft are diverting to Macau, get there quick! Ramp space is very limited and three diverting 747s will just about fill Macau to capacity.