@Juergen:
1. and 2.) would only work on specific fields. so any existing apps that use file fields would continue to use the original model
3.) would globally change the model, but that would also break South support :-(
I am very interested in a solution to make the file model extendable, but breaking South support is not really an option.
With the solution of extending by OnoToOne Relationship would also allow multiple apps to extend the model and not just one.
E.g one app could extend Filer to have a moderation workflow and another app could extend it to have advanced copyright information. With the full on replace the File model approach there could only be one of those.
@croepha:
I'll take a look at your fork soon. That looks like something that should be integrated in filer and was actually the base idea from beginning on. Unfortunately I never got around to code a nice api to it.
I'm not sure if it solves Juergens problem though. As far as I understood him, he wants to extend all files with extra fields. Your fork allows for added functionality for specific file types (e.g a PDF-Filetype that has extra pdf specific stuff) much like the currently hardcoded Image file type.