One of the things I can't cope is that the syntax of the pkg-plist
doesn't allow for a @dirrm which is allowed to fail. At this moment
the work-around is a "@unexec rmdir %D/foo 2>/dev/null || true",
which is hardly elegant nor a syntax which is worth being proud of
(but it works...)

Earlier suggestions with regarding to this complaint is that it
requires a set of tools to be rewritten to support it (pkg_delete
for example, which is in the base system and thus hard to upgrade).

My proposal is add the syntax already to the pkg-plist files, but
to convert it silently in bsd.port.mk to the old way. This way the
new syntax can be added the pkg-plist files, the new syntax can be
rolled out in the toolset when 7-CURRENT, 6.2-RELEASE, 5.6-RELEASE
and 4.13 (or when 4.x becomes unsupported) have been released and
then this patch can be undone in the bsd.port.mk file.

How-To-Repeat: 
    [~/cvs/ports/sysutils/newportsversioncheck] edwin@k7>tail -2 pkg-plist 
    @dirrm newportsversioncheck/etc
    @dirrmtry newportsversioncheck

    [~/cvs/ports/sysutils/newportsversioncheck] edwin@k7>make generate-plist

    [~/cvs/ports/sysutils/newportsversioncheck] edwin@k7>tail -2 work/.PLIST.mktmp 
    @dirrm newportsversioncheck/etc
    @unexec rmdir %D/newportsversioncheck 2>/dev/null || true