Use a CMS that's been around for more than decade which has all the features you want in a proper CMS (single sign on, WYSIWGY, multi-lingual support, a huge community of developers and service providers).
ie., Plone -- http://plone.org
(I don't say this to pick on Plone -- I'm a big fan of the TYPO3[1] CMS, for instance, which does lots of the things that he mentions very well, but the downside to that power is that it's insanely hard for normal people to pick up and use.)
[1] http://typo3.org
Selecting and using a CMS requires time, preparation and mostly importantly a budget. If you haven't considered the any of these, then you can't really afford a CMS.
Also, Zope based. I worked with Zope building large portals from 2000-2004. Worked, but not a very pleasant experience.
Zope is just a datastore that happens to be well suited for storing documents. Bad things happened because people did too much magic with zope. "With power comes responsibility" etc.,