[Zope] Read-only zope (not zope from a readonly Data.fs)

Hi, Is there a way to make zope run read-only(with whatever loss of functionality doing that implies)? I don't mean to prevent it from trying to write to disk (demo storage, -r), I mean to make it impossible to change persistent objects in the running Zope instance, something like disabling their __setattr__ (since it is hooked by Persistent, right?) Is something like this possible (by modifying ZODB source maybe?) TIA