I may be reading the original post incorrectly but it sound like you want to set the default umask to 000 for only one specific directory such that all new subfolders of users will be 777 and all new files within that folder will be 666. I don't know if you can do that as specified - at least not using standard Linux permissions. You can achieve this by doing something completely different however:
Install the following package:
And run the following command:
sudo apt-get install bindfs
That's going to need some explanation since it looks like a typo. What you are doing is using bindfs to mount a directory to itself with a "view" that has permissions defined in the bindfs statement. So all files will be 666 and all folders ( the +D part ) will be 777.
sudo bindfs -o perms=0666:+D /var/opt/newdirectory/users /var/opt/newdirectory/users
** Note that this is a view of that folder. If you were to unmount it:
All the subfolders will be 755 and all the files will be 644.
sudo umount /var/opt/newdirectory/users
If that works for you then you can add that line ( without the sudo ) to rc.local to have it run at reboot. You can also set up your own Upstart job to do this.
** Also note that this will work for Ubuntu up to and including 11.04 and so far it looks like it works for 12.04. It will not however work for 11.10 because of a sophomoric mistake in the dependencies for the bindfs package.