Summary: Has enough positions to pass.
I am letting Ben hold this document until comments from firstname.lastname@example.org mailing list are received. <future-pp2-specifier> and <pp2-defined-nonempty> can comprise any ASCII characters compliant with URN syntax in [RFC5234]. This reads to be as if RFC 5234 is the URN syntax reference, but it is not. Identifiers in the '3gpp2' NID are defined and assigned by the 3GPP2 or an agency appointed by 3GPP2 after ensuring that the URNs to be assigned are unique. Uniqueness is achieved by checking against the IANA registry of previously assigned names. This seems to suggest that IANA is tracking assignments within the 3gpp2 URN Namespace, but this is not true. Maybe just delete the last sentence above?