blokhead,
On a side note, it seems slightly odd that you would remove all of FOO and all of its dependencies as a result of removing BLAH.

Yes, it does seem odd. There is a 3rd unwritten rule that says

• You can't uninstall an item that has a non-existent dependency

In other words, if I get rid of BLAH without getting rid of FOO, I can never get rid of FOO. Also, there is no reason not to get rid of FOO because it will no longer work. I will confer with my co-worker to determine if there is an exception to this rule (a "must keep" list that says it is ok to leave a package in an inconsistent state). Alternatively, I will ask him if there is a technical restriction on removing a package before its dependencies since that would allow me to get rid of FOO but leave the other packages it depends on.