That is a great idea! I had all but decided to put the key switch somewhere discreet
That's the part that doesn't make sense.
If you're going to pay EXTRA money for a keyswitch button, why would you HIDE it?
If you're going to HIDE it, why not just use a simple, and CHEAPER, on/off switch inside the coin door?
If the keyswitch is going to be VISIBLE, why not just use IT as the shift button?
When the key isn't IN, the switch doesn't work, and you can't access the shifted functions.
When the key is IN, but NOT on, you have normal functions.
When the key is IN, AND the key is ON, you have shifted functions.
This does EXACTLY what you wanted the system to do, but eliminates the REDUNDANT button on the CP.
If you put the keyswitch somewhere accessible, but hidden (bottom of the CP overhang, for example), YOU can do all the admin you want, but nobody ELSE will even know it's there when the key is removed.
If returning to off (like the shift button you are planning to use) is an issue, use a MOMENTARY keyswitch.
The ROOT problem here isn't really the accessibility of the shift button anyway.
The ROOT problem is that the built-in code on the I-pac uses P-1 START as the shift key, and nobody thinks to change that.
That creates a condition where player 1 HAS to hit the shift button to continue a game, and can't do so without activating ALL the shifted functions.
I got around that by using my PAUSE key as shift.
If you hit the button, and HOLD it, you get shifted functions.
If you hit the button, and RELEASE it, the game pauses.
I've had kids from 3-15 play my cabinet for years now--without EVER locking it up.