Server Hardware for openplotter?

[glowntiger]

Hi Guys,
I had some Time during the Weekend. I have made a first Schema and PCB Design.
   
At the Moment on board are 1-Wire (DS2482-100) NMEA2000 (MCP2515 with MCP2562), 6x NMEA0183 (SC16IS752 with MAX3485) and 4x Optokoppler for 8-28V Input. On the Schema I have Consider the Moitessier hat.
Further I have add a I2C conn. for the In and output Boards.
Now I want to add the Powermanagement. My idea: 
I add a further Input. If you power this Input high (8-28V) the Pi starts. If you power the Input down, I switch an Input on the Pi to high, a script shuts the pi down. About a time delay (15s?) the power supply shut down. Now you can restart the System to switch to high.  Disadvantage: Between this 15s? you can not restart the Pi.
What do you think?

Further:
I have requestet some Cases. Alu and Plastic.

https://www.chinaenclosure.com/products/...AW-10.html (Alucase round about 40 USD)
https://www.chinaenclosure.com/products/...-wate.html (Plastccase round about 6USD)
Or something like this:
https://www.digikey.com/product-detail/e...ND/3681186 (Alu, round about 70$)

I think the cheap plastic Case is the best choise? If anybody whants to use another case it´s ok, but for the PCB i must know it for the holes and contour of the pcb….