Hi,
This may have been already thought of or worked on. But I keep running into import hiccups, such as trying to import phone numbers into Phone Number fields, and there is no support (that I can find) in Feeds or Node Import. If each of the contributed modules that supply CCK fields had a well-defined serialized format and provided some sort of function the importer could pass serialized chunks to, that would remove the need for each importer to hack its own support using undocumented internal structures. It could just be a serialized PHP array, but the important part would be that it was well-defined and documented.
Neal