Well friends, my journey has reached an important milestone. I'm pleased to announce that CLIX is now booting and seemingly operational on the InterPro 2020 system.
Battling with interrupts, dma, scsi and the mmu was worth it, as I've now been able to install and run the OS, and it seems like it's downhill from here. Focus will now shift to trying to get the other system models up to the same state (which may be tough for the C400 systems, given there's no documentation on their mmu), but I feel as if I've broken the back of this challenge.
The image below is the initial login screen for the EnvironV desktop GUI.
I'll post a more extensive update later and work on some notes for the wiki to explain how others can enjoy tinkering with this system.
OBTW, I'd love to do the "bannister in mame" thing, but I'm not sure I'll be able to get any web browsers working on this system. It does support an old version of X, but if I remember properly, there are various issues with its C library, signals and select support which make it a bigger problem than it may appear.