Why do you need so many switch's.? . . . Is this for a special purpose or just standard CMC machine operation.?

Unless your you plan on things like autotool changers or controlling many external devices then one PP is often enough by running limits and E-stop in series. After that then I'd look to the Pokeys device has it offers a cheap and simple why of doing it with massive amounts of inputs.

Personally I only use 24V thru all my Limits and E-stop system to eliminate any chance of noise issues causing false triggers. This is done thru relays or dedicated safety relay which shut things down at source or kills power in a controlled manner with the 5V signal from PC just used to inform control software an E-stop has occurred.