(1) The protocol would be more TLV-oriented to allow easier extension.
(2) The RFC would use RFC 2119-style language.
(3) The master file syntax description would be an XML schema.
(4) It might support some sort of cookie authentication.
(5) There would be even more butthurt about the TLDs.
(6) Dan Kaminsky would be part of the working group and at the point of consensus every coauthor would be required to sign an agreement about a yearly bitching quota.
(7) It would support STARTTLS and (D)TLS in general.
(8) Due to the additional round-trips required for TLS, the RFC would recommend to disable encryption by default. ;_;