TBD paraphrase and clarify
+Coming out of the software-related proposal by Jacob, which hinged on
+the idea of a global gcc / binutils database that kept and coordinated
+architectural encodings, was to quite simply make the mvendorid and
+marchid CSRs have WARL (writeable) characteristics. For instances
+where mvendorid and marchid are readable, that would be taken to be
+a Standards-mandatory "declaration" that the architecture has *no*
+Custom Extensions.
+
+This incredibly simple non-invasive idea has some unique and distinct
+advantages over other proposals:
+
+* Existing designs - even though the specification is not finalised
+ (but has "frozen" aspects) - would be completely unaffected: the
+ change is to the "wording" of the specification to "retrospectively"
+ fit reality.
+
> In an earlier part of the thread someone kindly pointed out that MISA
> already switches out entire sets of instructions [which interacts at the
> "decode" phase]. However it was noted after a few days of investigating