Comment # 24 on bug 1209594 from Luca Billi

Sorry to start sounding like a broken record but I'd like to reiterate that
set-keymap and set-x11-keymap are not orthogonal but they overstep each other:
they BOTH change all XKB* variables *and* KEYMAP.

Unless the toggle "--no-convert" is used that is.

Namely, if a user has configured KEYMAP != XKBLAYOUT, no sequence of
set-keymap / set-x11-keymap will ever be able to reproduce that configuration
and the user settings will be inevitably overidden.

That is not my case but I'm just pointing out a limitation of the current
approach.

Taking a step back, I don't know about the big picture but I'm wondering
about the role of the script "keytable".
If it is to just provide sensible defaults in case some settings are missing, 
maybe this logic might do the trick:

if KEYMAP and XKBLAYOUT are defined 
  do nothing (and preserve user settings)

else if KEYMAP is defined but not XKBLAYOUT
  set-keymap KEYMAP (which will also implicitly set XKB*)

else
  do nothing (current behavior)
fi