Dear Paul, Terry,
Amendments are applicable only to Common Text between ISO and ITU. Regular ITU Recommendations receive Corrigenda.
Formally, IGs have a lower status than a Recommendation. However, as mentioned before in this thread, IGs have been treated by the community that uses them as having the same status, in the *practical* sense. After all, the fundamental aspect is the stability of the change, and the use of IGs has allowed the work to progress more efficiently and consistently documenting the problems, than it would had been through the formal Rec. approval cycle. Of course, this is the treatment of IGs in SG 16 and, as pointed out before, does not need to be uniform across SGs. The issue of issuing corrigenda or not, or reissuing the Rec. in a new version is a common-sense decision based on the significance and extension of the corrections/modifications. Ideally, however, between version n and version n+1 the TSB would like that a period not shorter than 2 years be elapsed. This rule would not apply to Corrigenda. Please note also that while IGs are approved at a SG meeting, Corrigenda and revisions to Recs. are generally approved through the AAP in SG 16 (the TAP is only for regulatory-type recs, which seldom occur in SG 16), i.e., Consent at a SG or WP meeting, Last Call, etc.
If H.248V1+IGs is difficult to use due to the accumulated changes, maybe it is time for V2. It is the Rapporteur's group call. In this particular case, though, where we have parallel publication with the IETF, this republication has to be very carefully coordinated, probably leading to a different RFC number on the IETF side, with a quasi-synchronization of the approval process. As a matter of fact, all the IGs should also be made available to the IETF, maybe as draft-....txt (maybe it is already done, I confess I am not following up that thread).
I hope this helps.
BR, Simão.