Since our VMC is a big iron, we ran out with available inputs & outputs quickly, using the Mesa Cards.
An inexpensive choice is using the parallel port getting 17 extra IO's.
Getting some input and output from the parallel port is straightforward and well documented in Linuxcnc.
In our specific case we wanted more additional inputs than outputs.
We opted for the 0378 port giving us 4 Outputs and 13 Inputs.

We bought the C10 breakout board from CNC4PC for 28$.


We put the jumper for port 2-9 to become input.
We gave the board 5VDC with the Velleman K1823 kit (9 Euro) from our Machine 24VDC.
The diodes were not soldered.


We assembled both prints on a DIN Rail.


We started with the software(XML and .hal) LinuxCNC provided HERE.
We rewrote the XML and HAL file to get 9 additional inputs.


The HAL file is HERE
The XML file isHERE
Later on we integrated the XML file into our already existing PYVCP XML file.
It looks like this now:

Thank you LinuxCNC and CNC4PC; pretty easy done.