We've been down this road at least twice.
The last time I too sent F/C an email stating that I'd be a firm buyer of an O scale SU kit.
Never heard a peep.
As for F/C prior sales success, I'd suggest they look at what others have produced in resin, which is boxcars (I suspect there is a good reason that Clouser and Cameron and Chooch / Ultra Scale and Rails Unlimited have primarily produced boxcars/autocars).