Terry,
a few more years of LGB of A and we would all have scale length 1/22.5 cars, albeit Colorado prototype. Barry Bogs shipped sample cars to San Diego only months before the collapse in 2006 of the parent company. The rest is history.
I believe that a manufacturer would be biting off more than he could chew by releasing a fleet of White Pass cars as there are so many prototypes to make and in reality 1/22.5 scale is not as popular as previously. One would need to then choose the period to model/manufacture as cars varied over the years up to the current tourist railroad of today. One upside would be some of the cars could be marketed for other railroads, such as Sumpter Valley. World War 2 did wonders for the White Pass and would make an interesting period to model.
With the Colorado roads, one could make a generic coach and combine and market many cars. for the White Pass the number of individual cars is very long. Refer web link -
http://www.whitepassfan.net/whitepass/rollingstock/passengercars/index.html