A tricky part for many of us is having (or being able to procure) the requisite locomotives to go with the passenger car sets. S being S, availability of motive power is not as strong as, say, with O. Having stated this, there are some sets I would purchase in S hi-rail:
1. Broadway Limited smooth sided steamliners in FOM deco to go with the American Models streamlined K4s.
2. Broadway Limited circa 1950's to go with the AM GG-1s or PAs.
2. UP smooth sides to go with my (gray hound) L-AF Challenger.
Offering these passenger car sets might be an inducement for AM to do some reissues of the PA-PB sets (e.g., SP Daylight), F, and E units ... and MTH to do another run of their F units. Among other things, I am thinking of the need for B&O motive power for a Columbian. In theory, one could use the L-AF PAs for some of these sets, but the Gilbert style PAs will probably look a bit too crude next to the Golden Gate passenger cars.