Terry,
The concept of supplemental standards is a mechanism whereby the appraiser can be held accountable for compliance with appraisal standards inherent in an assignment that are not otherwise specifically addressed in the USPAP. Removing it could cause situations where appraisers would try to hide behind omitting these requirements by saying "Well, it isn't in USPAP, so I don't have to do it!!" You can argue that the requirements for Intended Use/Intended Users and Scope of Work could serve to render this element of USPAP as redundant. Who knows, maybe that's how it will go in the future. But I don't think we'd like the results of pulling it out right now. Read up on Statement 10 in the USPAP, and bear in mind that Smt-10 is not a suggestion.
The concept of Jurisdictional Exception is another handy feature in the USPAP that essentially prevents it from ever actually being in conflict with the law or other juridictional authority. Say a court issues a consent decree in a fair housing case that prevents appraisers from using certain descriptions or presenting certain factual data of certain type in appraisal reports; information that some people could argue would affect a reader's decision making process with respect to the appraisal. Without the Jurisdictional Exception Rule, appraisers would find themselves stuck between the law as interpreted by a court or other jurisdiction, and the disclosure requirements of the USPAP, which through incorporation by most appraisal regulatory agencies governs their appraisal licenses. This mechanism removes that conflict by yielding any specific portion of the USPAP in favor of established law or regulation, so long as it comes from a bona fide jurisdiction as defined, but without rendering the whole of the USPAP irrelevant to that assignment. Thus, there are no "non-USPAP" appraisal assignments just because one or more portions of the USPAP are in conflict with a law or regulation. I can't really see how Scope of Work could be written to actually conflict with the USPAP, so I can't see how this mechanism could be removed the way the Supplemental Standards rule could (someday) be.
Believe it or not, the contents of the USPAP are not added or otherwise changed casually. The ASB puts a lot of thought into it. As with any group of people engaged in such comprehensive endeavors, it's hard to make the right decision every single time, but their track record is pretty good from my viewpoint.
George Hatch