I don't think saying it "set a standard" is accurate. It could not fit everywhere a passenger locomotive should fit (Grand Central Terminal) and the biggest commuter agency of them all (NY State's MTA, operator of Metro North and the Long Island RR) did not operate them.

I do think it is worth of preservation because it was an important milestone in the evolution of passenger locomotives -- wasn't it the first US passenger diesel locomotive that could not provide steam heat?

If you mean designed from the drawing board to carry HEP in place of steam heat, then I think the GE U34CH of 1970 takes that title. The GE P30CH (1974) also came before the F40PH.

The last 6 E9As of the Milwaukee Road (built 1961) had an HEP plant from the factory, but only those 6 got HEP at the factory of all the E9s built.