Speaking of Daylight freight engines, how about an SD-9 painted in the "Kodachrome" paint scheme designed for the SPSF merger that never happened? It's not quite a Daylight, but the colors are similar and it would give the bright color junkies something prototypical to play with.
You know, as big of an SP fan that I am, I've never been that keen on the Kodachrome paint scheme; just the very idea of seeing SP engines with warbonnet-derived styling is somewhat off-putting to me (and the Santa Fe is also one of my favorites). As an aside I never cared that much for SP's experimental "Popsicle" paint scheme used on their TE70-4S MK rebuilds either.
I also like SP's Daylight scheme very much.
But frankly, if given the choice between Kodachrome and a fictional "Daylight" scheme that Forrest above alluded to I'll take the Kodachrome any day of the week, simply because that's what was used in real life.