Note to self:
The discussion of patching needs updating to reflect the possibility of changes associated solely with the identity, and not just with a layered distribution. An example of this would be product.conf or modules/layers.conf which belong to the identity. Unfortunately, it looks like the contents of the welcome-content dir will fit in this category as well. In AS 8 or later and EAP 7 hopefully we can move our default content into modules and reserve the welcome-content dir for user-provided content (or remove it altogether).