wasn't the page mode mmu the most important new feature? iirc this allowed for fully protected virtual memory, even for legacy applications.
(The 286 was enough for a PDP-11 style UNIX, and the 8088 could run a hobbyest-level one OK.)
i remember MWC coherent well! it was where i was first learned unix. :)
(except for maybe some vague memories of some unix like os for the atari st that i didn't really understand at the time, but those memories are extremely vague)