The fact that you feel compelled to provide for potential confusion in contexts where URIs are expected in XML languages is very troubling, if we read it as implying that CURIEs are intended for use in existing XML languages in places where only URIs are allowed today. We can't tell whether this is actually your intention, because the spec. is equivocal on this point. In section 5.2 [1] the (existing) 'href' attribute of XHTML is mentioned in the prose (worrying), but the _examples_ which follow only show CURIEs in the (presumably proposed for XHTML2 or HTML5 or . . .) 'resource' attribute (OK).

In this connection we find the prose about CURIEs the current RDFA spec. [2] troubling. The implication that CURIEs can be used in existing URI-only contexts is made explicit in one of the examples therein [3]:

<link about="[_:a]" rel="foaf:knows" href="[_:b]" /> 

and more generally there by the fact that the DTD for XHTML+RDFa defines several of its _new_ attributes, e.g. 'resource' and 'about', as containing URI references.

One can imagine an alternative proposal which made clear that it was only addressing the need for an abbreviated URI format in non-XML languages, or new XML languages, or new contexts within old XML languages, where _only_ such abbreviated forms are allowed. That is, a position taken _against_ any possibility the CURIEs might be used where URIs are called for in XML languages today. It would though have to acknowledge the possible negative consequences of success in going down this path, namely that ordinary users will not understand that the [-CURIE is not a universal alternative to URIs, and will start using them in existing languages where URIs are expected, causing tools to break and users to be frustrated.

All of this adds up to saying: please consider _very_ carefully whether the use cases/candidate requirements you have for the [-CURIE, i.e. a CURIE that can be used in an XML language where a URI can also be used, are really compelling. We note in this regard that we are aware of no requests for an analogous [-QName.