Not passenger cars, but I do wonder what would happen if 3rd Rail tried to get reservations for a few iconic steam locos in S scale. I've reserved a Rapido Royal Hudson in HO, and I'm also looking for the Weaver O scale version.
I'd absolutely be a buyer for a 3rd Rail quality S scale CP Royal Hudson, and it is a loco that has multiple paint scheme and detail versions, so the appeal might be broader because of that.
Other locos that might draw enough reservations? I'd think a UP FEF 4-8-4 might work, an N&W J, and the NYC J3a 4-6-4 Hudsons and PRR K4's. Some of these might have been previously released in brass, but I still think 3rd Rail Sunset could do them successfully.