When deleting an Extension Attribute, will the populating of smart groups based on the attribute fail? Or will there be a warning. True, I could test this, but there may be some best practices out there.

Likewise, when deleting a package used in a policy, shouldn't there be a warning of some kind? I think the Policy will basically just become 'empty', not delivering anything.

There is AFAIK nothing that lists these dependencies (which script/package/EA gets referenced where). A feature I miss direly.