I like your design.. Great if it is designed to be din rail mounted.
As much as I like to make things, at some point for me its easier to fork out a couple hundred. Time poor..
I have had this new module in mind.
Wrong link to the ethercat model. Couldn't find right one.
www.aliexpress.com/item/1005006434809743.html
I am wondering if this is EtherCat device PLC with I/O is less then the $500 devices referred to but offers the functions/features you are after.
I like how it has expansion boards.
https://ae01.alicdn.com/kf/S8027a5aa7da54e5d9bdaccca3b5e9f34G.jpg?width=800&height=800&hash=1600