I wouldn't be able to warm up to plastic BW inclusion as a "version" for collecting. There was simply too much chance at odd balls, no matter what Lionel "planned". ...maybe to judge a C-9/C-10 but otherwise it seems to mekinda redundant..(hey, spellwreck almost made sense!... seems to me, to be kinda redundant; is what it said before it changed at random) I'd sooner go for the slight color differences within the major shades normally collected.
Riveted brakewheels would be another story though.