The power block or mausberry (or similar) is the key for safe shutdown of the raspberry pi. The switch that gets wired up to one of those RPi shutdown circuits can also shut off your cabinet or other components, but the trick is that the Raspberry Pi would need to be powered separately from the components of the cab. If you have your pi's power supply connected to the cabinet power, and the main shutdown switch powers off the cabinet, the Rpi would be cut off instantly along with the cab power. So basically you have to power the Raspberry Pi upstream from the cabinet's switching power supply.
My original Defender cab was set up like that so that it could have an accessory plugged in and working even if the rest of the cab was powered down, so that you could plug in a lamp or soldering iron or whatever and work on the cabinet without running an extension cord to it.
So basically if you have the cabinets power going into a switching power supply, you could add in an outlet for the pi's power adapter upstream from the cabinet's switching power supply so the cab's power and the Pi's power are separate. I think then you could use a two-pole switch
to control the cabinet power, and as a switch for the power block (or whatever).
I haven't wired this same thing up myself, but it's what I've been planning to try sooner or later.
Alternately, you'd have to create some kind of relay so that once the PI is powered up or down, the rest of the machine would also be powered up or down. I've seen some people do this with breadboards, but seems more than what I need so I haven't looked into it.