John, a couple of comments:
1. Need to be a little careful with the specialized vocabulary used by the preservation folks at the NPS. The C&TS is a long way from achieving "Landmark" status. Just a year ago the railroad finally became a "National Historic Site of National Significance". Reaching that status helped the Friends win a $300,000 "Save America's Treasures" grant toward the rebuilding of 463. "Landmark" status ought to open even more federal funding opportunities.
2. By law the NPS delegates application of the Secretary of the Interior's Standards (SIS) to the State Historical Preservation Offices. If you review the text I posted recently on the NGDF from the Friends report on this subject I think this becomes clear.
3. As I also pointed out in one of the NGDF posts, the SIS relate well to buildings and structures, but not to rolling stock and locomotives. Try digging into what the SIS says in detail about "mechanicals" and apply that to locomotives. Again, consider the unintended consequences that might ensue if building preservation experts were invited to apply their standards and guidelines to railroad equipment. Do you really want to go there?
4. I think the "something better" you are looking for already exists at the C&TS in the way that the Friends deal with the historic non-revenue equipment in cooperation with the Commission and the existing "benign" oversight by the SHPO's. As I've already said in another post, that's not to say all is perfect -- 489 and MW02 being examples.
5. And, at the risk of setting off another argument over the historic "versimilitude" of the Chama yard, why doesn't anyone (SHPO or rail-fans) object to the ugly, mall-parking-lot, overhead lights outside each end of the engine shop? Certainly, good lighting is required for safety reasons, but couldn't the railroad find lighting fixtures that are more historically appropriate and that still would provide good task lighting? We object to too much silver trim on 489, but look right past those weird lights
.