Consider a policy that includes Reliable Messaging, Header Encryption and Signing.  It seems clear that the Reliable Messaging headers should be added first, the headers encrypted next that finally the signature created and affixed.  At the receiving end, the signature should be checked first, the headers decrypted next and finally the Reliable Messaging headers processed.  This implies that the Policy assertions be processed in a definite sequence.

The framework document says:
"Assertions within an alternative are not ordered, and thus aspects such as the order in which behaviors (indicated by assertions) are applied to a subject <http://www.w3.org/TR/2007/PR-ws-policy-20070706/#policy_subject> are beyond the scope of this specification. However, authors can write assertions that control the order in which behaviors are applied."

It seems to me that this is a fairly common scenario and it may be good to show an example in the Guidelines document of how such an ordering assertion may be authored.