I am currently employed at gameworks. I can tell you this: Each Gameworks location has ZERO say in what machines they get. We don't ever purchase a machine and therefore have no "game budget". Rather, all machines are dictated by sega. As nice as a IIDX machine would be, it's not going to happen. Someone at Sega would have to have a IIDX machine floating around somewhere and decide to put it at a gameworks.
tl;dr Gameworks will not get any arcade machines based on what customers say. It's all up to SEGA |