I think, the first one is achievable with the
ACL (access control lists). The second one appears not to be possible atm, as fas as I know, but I'm no DW guru. ;) And the third is easy again:
Namespaces, they are like folders, aktually they are (DW relies on Files not on an database).
If it's an to "concentrated" answer, don't hesitate to ask further questions.
Cheers
BlackFog