Who are the "other ones"

As I read this, I really feel for Dan, but also understand the "why's" of the rules.
So, if there was a "Historic Locomotive" waver within FRA rules, what would be the criteria, and what would the other locos be?
A loco in question would have to see limited use, and be preserved for its "historic fabric" more than for its functionality (i.e. it wouldn't be eligible if its primary use is pulling trains, so neither of the K27’s would not be eligible)
This is a significant issue at the various rail fairs (Sacramento, Durango, Baltimore) all of which have FRA regulated demonstration railroads, but also have locos which should never be expected to meet FRA rules. (and are only operated for rare, occasional demonstration use)
In addition to Eureka, I would nominate:
John Bull at the Smithsonian
Inyo at the Nevada State RR Museum
in the Future, CP Huntington at CSRM
Any of several early engines at the B&O
Claus Spreckles in Hawaii
In all cases these engines are used purely as demonstrations. All are used under a high level of professional care and supervision. Inyo is used at a greatly reduced boiler pressure. All are being conserved rather than used.
The concept of a historic exemption could be reasonably extended to historic freight cars (what happens if K brakes are outlawed, and do you really want to put reflective tape on all the 3000 class boxcars on the C&T) passenger cars (we displayed (and operated)an 1882 SP combine which didn't have air brakes at Railfair in 1999 or some early diesels (ditch lights)
Randy Hees