Red borders in edit mode on modified containers

Cf parent JIRA.

If we introduce a new "blank" workflow state, it would then be quite nice to be able to immmediately see the container which was modified (so on a red page which are pages which were already validated once).

So could we imagine red-lining the border of modified container =which have a different version from the live one)? Is it complex and time-consuming in term of performance? Or is it only a simple check on the versionid which is done in all the cases when rendering the page?

This will give an additional information to the author and will avoid him to switch each time to the compare mode to know which container changed compared to the live published mode.