Everything in a CMS should be versioned. Zope 3 has undo, but that’s not object-specific, it’s system-wide, so if you make a fatal change and then do ten or so things to another object, you’ve lost your undo for your fatal change.

Everything: content object, images, stylesheets and especially products (or modules, InfoCMS’s equivalent) should be version managed. The user should be able to just select from the last X versions and branch from there, without destroying newer versions.

Zope 3 does have a versioning package, apparently but it’s unclear what the scope of the facilities is. CPS apparently implements it on Zope 2. InfoCMS used to version page object content, but I honestly can’t remember if I kept that feature when I reimplemented it all with page objects.

Edit: Zope 3 version control is definitely happening in the right way. People have the same ideas as me and while the code looks to be in it’s early stages, it seems to implement much of the required functionality. The critical thing is: will implementors make use of it for their products?