Scrambled as a sketch for my own planning of my system from info found in comments on the question:

'Could one construct a Rutt-Etra style scan processor from Cadet modules only? .. '

on the LZX Video Synth Community on Facebook:
https://www.facebook.com/groups/lzxindustries/permalink/777873335717322/

A more recent thread on the LZX Video Synth Community on Facebook (that links to this rack) explains stuff a bit further:
https://www.facebook.com/groups/lzxindustries/permalink/1142573835913935/

Other resources for smaller system configurations and explanations:
https://rutt-cadetra.blogspot.com/2017/12/a-rutt-etra-design.html
http://vasulka.org/Kitchen/PDFEigenwelt/pdf/136-139.pdf
https://ernavk.wordpress.com/2018/02/13/lzx-cadet-based-scan-processor/?fbclid=IwAR33dcm1e8wnL
hFbnv_W-EiUFgrrxoNva-bSHCgCEp4d7j5URKY9OhViMY

also check out this (long and dense) documentation from an event held exploring the Rutt-Etra Scan processing system and its contemporary uses:
http://www.bentoncbainbridge.com/portfolio/global-groove-2/