"Restricted" page editor

See https://community.jboss.org/wiki/RestrictedPageEditor

A customer is willing to give the ability to many different users to edit pages. Those users would require a simplified page editor and be constrained to simple actions. In particular, users should not be able to compose complex pages and risk to break the layouts.
The layouts should be restricted to what is available from the "Containers" tab of the editor.

In particular the 2 following scenarios should not be possible:

Scenario 1: User should not be able to put an application above/below the 2 column layout (As this break the pre-defined layouts, suddenly the user is able to have a single column representation while this may not have been provided):

Scenario 2: User should not be able to put a layout within a layout (only above or below existing ones)

Proposed solution
Add an option in configuration.properties for a restricted page and layout editor. This would apply across the whole portal.
gatein.portal.pageeditor.mode=full (default) | restricted
gatein.portal.layouteditor.mode=full (default) | restricted

Applications could only be added to predefined layouts (and not directly on a page).
Containers could only be added to the root of a page (not inside another container).