Honestly, I never put wheels on mine. As easy as that would make moving them around, I always go for the leg levellers. You know, the pads with the studs that you screw into the plate to adjust. But I also have carpet. So wheels may be good for you if you have hardwood floors or something you don’t want scratched up.
As far as design, it depends on the type of games you’re wanting to play. If you’re into the street fighters, and the Mortal Kombats then best advice, minimum 2 player control panel, 6 buttons each plus the 2 joysticks. You can map them to play almost anything in that configuration.
OR… Here’s an idea, since you have a CNC machine… You could build your cabinet, I’d design it around the type of monitor you’re planning on putting in it. Then, you make a control panel system that you can add/remove with latches. Have your keyboard encoder mounted on each control panel, then your entire control panel becomes plug and play. Unplug the usb, remove control panel, install Bigger/Smaller control panel, plug in USB, you’re back up and running. Have like a 4 Player, 6 button each, control panel for when the friends wanna come over and hammer on some xmen, or a simple ms pac type control panel with a joystick and couple of buttons to play the real classics. Even set up a control panel with a trackball. When you need it, unplug, detach, attach, plug in.
The easy approach for access would be a back door. Since you’re not building a machine for a route, I’d make the front coin door area my access panel. Like, put the entire thing on a piano hinge or hidden hinges or something. When you need to open it, you dont 'even have to move your cab, just pop open the front.
Computer, Raspberry Pi, multi boards, this day and time, so many ways to run an arcade machine it’s not even funny. The Jamma multi boards are the most maintenance free way of doing things. Plug it in, and go. No updating, etc. Then there’s the harder method which is emulation on a PC… That can get rough on you in time tho. Computers can be so finicky… And then, there’s the Pi. That’s a nice lil’ system for arcades. Buttons are a touch intimidating to setup if you’re running more than MAME, but right out of the box mame configs work on most encoders.
Power could be as easy as a power strip inside the cab, and a PC power supply, or switchable power supply.