Re: enriched-mode and switching major modes.

[Richard Stallman]

    I now believe that Enriched mode should be temporarily disabled when
    switching major modes and later re-enabled by post-command-hook.

I think you are on the right track, except for the detail that
post-command-hook does the job too late.  enriched-mode ought to get
reenabled as soon as the new major mode is set up; it should not wait
until the command finishes.

One way to make this work is by adding a feature to run-mode-hooks.
enriched-mode's change-major-mode-hook could then do someting 
to tell run-mode-hooks to reenable enriched-mode.

Want to try that?