Since it was possible to create 2 additional models for the 747-400 cockpit, why not a BCF/BDSF model? It would nicely complete the package.

Just have someone create a cargo livery for the 747-400 base model. You'd have use the Load Manager tool in passenger mode, and load the approximate number of passengers for the same amount of cargo (all you need to do is match the payload, which is displayed). It's the same exact model, really, and I'm guessing that's why they didn't do it. The separation between the -400 and the -400BCF is a window delete and a cabin gut. None of those are visible on the external model, through creating a model. All you need is to blank the windows out on the texture and you're good to go.