Next question: if I use the plywood instead of 100% hardwood, will there be any weakening problems where I route it down to 1/4" for the SANWA buttons? The joysticks won't be an issue as they will be top mounted.
SANWA's need 1/4" mounting surface? That seems extreme, but if this is routing on the underside I don't see any problem with that.
It could get a little messy, but sand paper will clear that up. I think part of that will depend on the plywood quality you get. You can always ask some of the old guys at home depot about routing out the plywood.
If you are routing out the top the only concern I would have would be large splinters coming up off the wood leaving it uneven. You can always check how thick each layer of the plywood is by checking out the edges. But still, 1/2" of wood routed out for sanwas........ ridiculously small clearance for those things.