Awesome stick so far and I still like to see your project to a great completion.
I do see what you mean by cheap wood. Plywood is not a bad product to work with, in most cases its stronger than other materials.
I used plywood in some of my stick builds where I needed to reinforce my stick case. So far the carpentry are sound, and this stick case looks almost furniture grade. When you are done you might want to add a clear coat finish to protect and preserve that nice paint job you have done.
And I see you used Happ or IL buttons and joystick (more on this in a second). You can easily reinforce the whole top panel by adding a layer of MDF or Medium density fiber board underneath. Plywood as alot of strength from having multiple thin layers of wood glued, with the grain of the wood going in a alternating pattern (one layer goes up and down while the next goes right to left, then the next goes up and down again)
MDF is reformed board of small wood particles glued together with a plastic based glue, semi-strong but unlike plywood is not subjected to warping, flexing and bending due to tiny particles. MDF cuts and drills almost like plastic, and needs to me primed before painting.
Idea here is if you layer 2 different materials together (Plywood + MDF) or even 2 layers of plywood, they will gain more strength than what a thicker piece of wood can’t do alone.
I suggest you glue to that top panel (underneath if you want to keep that paint job, since MDF needs to be primered first before it is painted) ether another layer of MDF or another layer of Plywood if MDF is not available. This will reinforce you top panel very well. And maybe a Plexy layer on top to protect that top layer from wear. You choice in Arcade joysticks and buttons will mount well enough in thicker material.
Optionally you can take this a step further and add some additional wood or metal supports to make that panel even tougher.
and D3v is on the ball with using a MC Cthulhu + Imp/ DPDT (double pole double throw) switch, alternatively you could use a ChImp and you lose the Dreamcast support but you get a slightly easier mod. This is assuming that Xbox 360 PCB is common ground. Microsoft brand and Madcatz brand Xbox 360 pads are Common ground (except for the RT and LT) which appear you are not using anyways. Top of that, using Toodle’s 2 golden rules of Multi-console mods, you can chain almost an unlimited number of PCBs together.
The 2 golden rules are
All PCBs must be connected to common ground
All PCBs must be powered