I would re-think the mouse buttons, if you are right handed, move them both to the left so you can use the buttons and keep your hand on the trackball as opposed to having to keep switching hands depending on what you want to do with your mouse/trackball. Also seems like the trackball and the player 2 and the the restricted joystick are quite close together, could be trouble with Missile Command, Centipede, etc., you could end up slapping into those sticks.
As for the extra joystick with the mounting plate, why not just put the plate on your one player stick when you need it instead of buying an extra 8-way? I can see having a dedicated 4-way, but the 8-way I don't get.
Your spinner is going to be really far away from your player 1 control buttons, could make it awkward to play some of those games I think.
It looks like you have a good start, but things seem really close together and compact, is space an issue with your CP?