When going through 'My Issues' I found this one again...

I'm sorry I haven't got a decent implementation for this.
As Bart Schaefer noted on zsh-users some time ago, best would
probably be to implement this within the accept-line wrapper,
that we are using. I've been at it for ~45 minutes but I
was not able to resolve this in a way that I would be happy with.

In fact, I was quite unhappy with the results I had.

Then I wanted to go at a half-assed hack so that we could at least
close this bug, even if it wasn't perfect. While doing that for
about half an hour, I got so fed up with myself for even considering
something like that, that it caused me to delete my topic branch
that held the code.

Marking as deferred for now.