What we are planning is to have the concept of "required" properties (as opposed to mandatory). An object will be allowed to exist without any "required" properties, but will not be created if it is missing any "mandatory" data. In this way, we can allow content to be added via CIFS, WebDAV and for it to be specialized to a different content type.
However, some services will not be allowed to operate on an object unless its "required" data is complete (e.g. workflow, check out). In the web client, required fields will be collected at creation time (upload or inline). In CIFS, a virtual link to the properties page will be created for objects needing metadata.
Probably 🙂