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Thanks for the pointers to both of these... I wasn't aware of either. I see argparse has been recently approved for Python stdlib inclusion, too: http://www.python.org/dev/peps/pep-0389/ Congratulations!
As far as I can tell, genzshcomp is parsing the output of the help command to reverse-engineer what the allowed flags should be. Assuming that only one space occurs between the arg and its metavar, this should work 99% or the time... I'm not sure if there is any attempt to be clever when the formatting is ambiguous. But given that the opt parser already contains the structured information, life can be made easier by writing out a more readily parseable format.
Here's an example bash parser function and its usage, for a further-simplified form of the above format where each arg (long or short) gets a line of its own and the arguments are indicated by a separate word as in the current output:
Example input:
$ foo --help-options
#OPTPARSE_FORMAT 0
--version
-h
--help
-r REGEXP
--regexp REGEXP
-s N
--start N
-e M
--end M
-f FILE
--file FILE
and the parser/completion functions:
function _optparse_getargs() {
	local opts cur prev
	COMPREPLY=()
 cur="${COMP_WORDS[COMP_CWORD]}"
 prev="${COMP_WORDS[COMP_CWORD-1]}"
 PREVIFS=$IFS
 IFS=$'\n'
 for line in `1ドル --help-options | egrep '^-'`; do
 opt=`echo $line | sed 's/^\(-[^ ]\+\).*$/1円/'`
 argeq=`echo $line | sed 's/^--[^ ]\+ \([A-Za-z0-9]*\)$/=/'`
 if [[ $argeq != "=" ]]; then argeq=""; fi
 opts="$opts $opt$argeq";
 done
 IFS=$PREVIFS
 unset PREVIFS
 opts=`echo $opts | sed -e 's/^ *//' -e 's/ *$//'`
 if [[ ${cur} == -* ]] ; then
 COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) ) 
 if test -n "$COMPREPLY"; then
 return 0
 fi
 fi
 return 0
}
function _foo() {
 _optparse_getargs foo
 return 0
}
complete -F _foo -o default foo