[Zope-CMF] Allowing content authors to only delete some content from a folder

[Heimo Laukkanen]

At the moment deleting content from a folder in CMF ( and so also in 
Plone ) requires that users have a Delete objects permission in that 
folder. Unfortunately that also means that users can delete from the 
folder any object.

I would like to have the possibility to allow users to delete *some* but 
not all objects from a folder - for example based on whether the object 
is published or what type is it etc.

Currently the only way that I can think of implementing it is to do my 
own content types with ArcheTypes and add manage_beforeDelete-method 
that gets called and throw exception in situations that I don't want 
object to be deleted. These rules could be written first inside the 
classes but later on moved to be configurations inside the CMFSite / 
PlonePortal.

Does anyone else have a better idea on how to implement this?

-huima