Upgrade scripts *already* need to do this, Dave.
The restriction is that instead of writing something like
CREATE OR REPLACE PACKAGE FOO ...;
CREATE OR REPLACE PACKAGE BODY FOO ...;
CREATE OR REPLACE PACKAGE BAR ...;
CREATE OR REPLACE PAKCAGE BODY BAR ...;
You must write:
CREATE OR REPLACE PACKAGE FOO ...;
CREATE OR REPLACE PACKAGE BAR ...;
CREATE OR REPLACE PACKAGE BODY FOO ...;
CREATE OR REPLACE PAKCAGE BODY BAR ...;
The first example can lead to dependency errors (as Andrew so painfully learned), the second can't.