I've built 3 or 4 MAME cabinets and the frontend I use is Kymaera which allows you to switch between as many emulators that you install.

It's easier to restore a used cabinet instead of making your own from scratch. 3 of my cabinets I bought from Todd Tuckey. They were empty cabs he wanted to get rid of. Sometimes you can find them on Craigslist.

Keyboard encoders: https://www.hagstromelectronics.com/

Encoder for buttons, trackballs, spinners, joystick https://www.ultimarc.com/minipac.html

Buttons, joysticks and other parts http://mikesarcade.com/cgi-bin/store.pl

LCD Monitors (and other arcade parts) https://na.suzohapp.com/wp/search.p?Q=lcd+monitor

Arcade artwork, control panels, coin doors etc https://quarterarcade.com/

I do. It's not bad.

That's why you see some people have a coffee table for a control panel LOL.

That's not my cup of tea...