For god's sake, please nobody repeat the mistake we at openplans.org made: implementing the historical revisions feature by combining CMFEditions with RichDocument (or anything else folderish). Why? You end up with a complete pickled copy of the folderish page and all its content (in this case, uploaded attachments) for *each* revision. This makes our history views insanely expensive. Now we have to dig ourselves out of that hole.