Priority Feedback

Section 4.1: Schema defaults

I don't have any issues with the schema default mechanism.  My preference
for default values would be "extension restriction" or "#all" foe
blockDefault, "unqualified" for attributeFormDefault and elementFormDefault,
"" for finalDefault.  If everyone agreed what the schema defaults should be
(which I don't envision), then the schema defaults could be removed.

Section 6.2: Redefinition

I cringe at this one.  It would seem to me that the objectives of
redefinition (especially as in migration from v1 to v2 of a schema) could be
accomplished readily using XSLT or other processing in the preparation of
the schema and this complexity doesn't need to be pushed to the parser.

Multiple inclusions:

Implementing the deep comparision involved with tolerating multiple includes
of the same file in the same context (since you could include the same
resource sans targetNamespace into multiple targetNamespaces) seems
excessive and unnecessary.