I have hacked CC629 so that:
one product can contain multiple digital files. This allows, for example, one to sell an "album" of several files - each file independently downloadable.
will override the above when assigning one of the multiple files each to an option. This allows, for example, one to sell an audible book (available in multiple languages) - the customer having selected an option for an available language (or an audio file, choosing a filetype of MP3 or WAV).
This is not a plug-in -- it's core code edits. I am not convinced CubeCart has (or could ever have) the requisite hooks. (But who knows?)
I need a beta-tester. Post a PM.