Unpublishing should include modified children of the unpublished node

When moving published items between trees there can sometimes be inconsistent states.

Reproduce
Consider two websites travel and sportstation where a new test page has been added to the sportstation tree. Make sure all pages are in a published (green) state.
Author instance

| - travel
    | - about
    | - tour
| - sportstation
    | - about
    | - tour
    | - test

Move the test page under the travel page.
Author instance

| - travel
    | - about
    | - tour
    | - test
| - sportstation
    | - about
    | - tour

The test page should now be in a modified (yellow) state. However on the public instance the page remains under the sportstation tree.

If the user then unpublishes the entire travel tree (unpublish incl subnodes) the test page will remain under the sportstation tree on the public instance.

| - sportstation
    | - about
    | - tour
    | - test

Expected
I would expect the test page to be removed from the sportstation tree.

Actual
The test page remains under the sportstation tree after the upnublish incl subnodes.

Notes
I'm not exactly sure how this should be handled. Maybe a move should trigger an unpublish or at least prompt the user about doing so.
Maybe moved items need some kind of tracking flag. Saying it's modified is not enough. Perhaps there should be a metadata property which has mgnl:moved=true until the item is published. This flag could be used to prevent this case from occurring.