I have created a patch for netcfg to support tunnels, such as sit tunnels for IPv6. The included example would act similar to the rc.d script found at https://wiki.archlinux.org/index.php/IPv6_-_Tunnel_Broker_Setup
You can find this patch as a git commit on https://github.com/kylef/netcfg/commit/e6b95df3a80a92480a5ee062a13f5c844802098a This is commit e6b95df3a80a92480a5ee062a13f5c844802098a on the branch 'tunnel' on the 'git://github.com/kylef/netcfg.git' repo. I have no where I should submit this pull request, this mailing list seems most related place I could find.
