Hugh (& Lou, and other interested parties) -- I haven't kept up on the conversation, as I'm trying to sort out a few other things before freeze. I will try to catch up and comment over the weekend, but perhaps you could give a summary of what you'd like discussion on? One note: off the top of my head it seems @include and @except should indeed be mutually exclusive. Even if having both makes sense, it doesn't match their use on <moduleRef>, where they are mutually exclusive.
Just to follow up: I would really appreciate some discussion of this. I did stuff to make it work, but it's a little hacky. Intuitively, it seems to me that @include and @except should be mutually exclusive—if you have one there's no need for the other. Practically, given RelaxNG as a pivot format, I decided to use both together, because it makes explicit what's being excluded, and therefore clear to people extending TEI how to exclude additional namespaces. Maybe it's better to do some "magic" if it's more logical in the ODD though?