BTW, to convert the output of pkg_cutleaves to category/portname form, you can use this pipeline:
$ pkg_cutleaves -l | while read p; do pkg_info -q -o $p; done
With a little more work and another stage in the pipeline, you can use this to automatically generate the lines in a metaport like killasmurf86's:
$ pkg_cutleaves -l | while read p; do pkg_info -q -o $p; done \
| awk 'FS="/" {print "RUN_DEPENDS+= "$2":${PORTSDIR}/"$1"/"$2}'
OK, maybe you can't completely autogen the metaport. In some cases, you're still going to have to hand edit the name of the file Make should look for in deciding whether a port needs to be installed. But hey, this gets you 90% of the way to your goal.
HINT: to find the lines that need hand-editing, construct a similar pipeline using the 'which' command to check whether there's an executable on the path with the same name as portname.