Development of Creative Commons licenses

["White, Phil" <Phil.White AT rjah.nhs.uk>]

Greetings. 

I wonder if I could pose a question on this forum? I am contemplating
choosing a CC licence, but having some problem choosing exactly which
one to apply - I will try to outline the problem...

The 'work' involved is a collaborative group effort. As such, there may
be one author, or there may be many collaborators. Although I want the
work to be available to all, I want to retain control over the work
itself - and this seems to present a conundrum. To try to explain, this
is my current solution (though I don't like it):

I act as publisher/distributor. Authors/contributors assign all rights
to me on submission of the work, and assert that they have the authority
to do so.

I release the work, published on a Wiki, under a CC licence. The work is
to be attributed by reference to the URL and date the document was
copied.

Now the problem: This is a living work. The world changes, so a
Derivatives licence would be logical, BUT I do not want derivatives
being used or distributed from anywhere other than from the original
site - which implies a No Derivative Works licence. But for the work to
have any relevance for me, it has to be published on a Wiki, which is
constantly changing. Are these two situations incompatible? How can I
allow derivative works "only on the condition that it is published on my
Wiki"?

Best regards,

Phil.