Just a placeholder for myself to investigate implementing the import functionality as separate feeds processors. This would allow results to be derived from HTML (feeds querypath parser), XML (feeds xpath parser), JSON response (feed jsonpath parser), CSV/XLS (native feeds doc parser), etc, etc... it's pretty incredible the range of imports that this could support.

While I haven't put as much thought into it, I believe Views might be the best option for export, as there are lots of display plugins like for DOC/XML/CSV (views_bonus), or many other datasources like JSON, RDF, XHTML (views_datasource)

The tools are all there, but perhaps there is a niche within these other modules to have exportable definitions, as currently, each requires quite a bit of setup (defining query paths for import from a given type of source file, or XML structure for a given standard of output/export).

Anyhow, I'll try to do some thinking on it later :)