This is a nicer design which has a Eurocard size board, DIN41612 connector, and a Z80 processor. It communicates through serial ports, and only draws 5V, +12V and -12V power from the DIN41612 connector. So it can be easily adapted for other buses with those rails.

The crystals look a bit precarious, I would change them for lower-height versions.

There is 8K of firmware, implementing a graphics terminal. I'm sure the design could be greatly expanded.

It uses two Mostek MK3801 chips to provide I/O and timers. These were never popular and are hard/expensive to get in 2022. This adds a hurdle to recreating this board.

One MK3801 is used for parallel I/O and a computer terminal. The other is used for a keyboard and can be omitted if there is no keyboard. Serial ASCII keyboards are long obsolete so the second MK3801 is unlikely to be needed.