Re: Shared directory behavior
ahh, after rereading, don;t worry about samba. I was under the impression you wished to share the directory over your network. anyway, just makes the job all the easier.
also in terms of Deleting/creating, you might also want to look into the sticky bit. it allows users to only delete files on which they are the user-owner, even if the user has the write privilege.
that way everyone has write based on their group membership in Dev, and can add to eachothers files, but they cannot rename or delete files without first taking ownership (if they are able).
sudo chmod +t <path to dir>
Things are rarely just crazy enough to work, but they're frequently just crazy enough to fail hilariously.