If #3 is done, then it needs to be translated both ways. Best to have something consistent though, i.e., date field in both or neither.

GEDCOM does not have a separate date field for sources, and I believe it is intentionally unstructured to maximize compatibility. As long as FTM/Ancestry export a valid GEDCOM, then it makes no difference, I think, what's done on this end, as long as the information synchronizes so people moving from Ancestry.com don't have to spend countless hours doing what a computer could do in seconds.

http://homepages.rootsweb.ancestry.com/~pmcbride/gedcom/55gc...

Here is the relevant field:

SOURCE_PUBLICATION_FACTS: = {Size=248}
When and where the record was created. For published works, this includes information such as the city of publication, name of the publisher, and year of publication.

For an unpublished work, it includes the date the record was created and the place where it was created. For example, the county and state of residence of a person making a declaration for a pension or the city and state of residence of the writer of a letter.