Does DC plan to have site developer make their own management interface?

The site-developer wouln't mind using the management interface for their work, but most of them will reject the common users using it. Of cause there were security issues also.

Allow the site developer to make new interface on specific branch of the object tree will easy their jobs.

Using basic Zope, yes. If you want end-users to manage content in any way, you have to create the end-user interface and expose the underlying management interface through it as you see fit. The Content Management Framework (CMF) Zope product (zope-cmf@zope.org) is another approach for portal-like environments. CMF is specifically designed to delegate content management using a common, more user-friendly interface. -- Loren