The file updmap is intended to be edited when you add some Type 1 fonts to
TeX.  It seems to me that qualifies it for a %config marking.  So that
upgrading tetex-dvips won't lose any changes.  (Again.)

And yes, I had to remove japanese.map from updmap besides adding my own
maps to it.  Otherwise dvips dumps core, as explained in bug 32134 and
others.  But this is a different issue, though related of course.