It seems entirely reasonable that there needs to be a version available
that's precisely as-published, for legal (and quasi-legal) reasons, as you
say - however, that's the version produced by the RFC Editor, and not the
tools version (which is already non-normative, technically, due to the
markup).
What I'm driving at is whether the right way to handle errata is by
changing the document on tools (perhaps by diff submission). This should
reduce the mechanical workload of errata handling to near-zero, and leave
the judgement calls of whether to accept them as the cost.