But Esc is used as cancel in the standard RPG Maker setup too, it is both a Menu and Cancel key in a standard setup, all I did was add the use of WASD and SpaceBar because some people said they wanted those instead.
I haven't seen that many setups that used Z and X, personally, though I have tried them in an earlier version of my game and I got a lot of complaints from people claiming they had to punch every key on the keyboard until they found the "Enter" command.