Retrofitting HURCO BMC30

Why 2 of 7i92? Why 7i80?
I used a single 7i92, 7i74, several 7i70 and 7i71, and 7i77.
Since there is no easy to find 7i77, i would use 7i92TM plugged directly into a 7i85, then a 7i83 for the analog outputs, and add 7i70 inputs and 7i71 outputs as required.
All of those can be easily found, well if there is no 7i92, get a 7i96S, adds another sserial and some inputs and outputs, and some stepgens you probably have no use for, but will come handy if you ever have to change drives, new ones can do step/dir, most of them.

Not sure as it was a long time ago, but i am pretty sure you can have everything working with just:
7i92TM plugged directly to 7i77 and a 7i84 connected with a cut in half LAN cable.
That is 64 inputs and 32 outputs, should be more than enough.
I did it the way i did as i am a control freak and like to have everything at a glance so 7i70 and 7i71 having LED for each IN/OUT helps with that. And if you look at my retrofits, all have every IN/OUT on screen ... yeah freak!