Hey Andrei,
my dream setup would be one big textarea with an advanced wysiwyg widget. The content would be saved as regular html in the db. The author wouldn't need to know html.
I would tell beginners: Don't define the way different parts of your content are getting displayed, but define what these parts represent. An example structure: Header1, Header2, Content1, Content2, Image1, Image2, Table1, Table2 etc. The author could centrally define and alter the style of each class. As long as the structure is well defined it can easily be exported into xml and be mapped to pdf, docbook and maybe even word etc.
So I don't want to tell people how to format things differently, which is what wiki does, but give them a wysiwyg widget and the content would be saved somehow intelligently.