Allow different feeds to update same content type

My use case involves matching records being imported from two different systems, an HTML feed and an occasional bulk update with a CSV file that imports different fields.

With the GUID's for both feeds properly set to the common unique key and both feeds set to "Update", the second feed will create new content records rather than updating the old ones.

Would it be relatively straightforward to update solely off the GUID field in the feeds_node_item table rather than also referencing the field ID? Essentially an option to base the update feature off a key field in the content type, or off of the content type and guid rather than off the feed id and guid.