I have decided to get a few of us together to put together a D6x Module that will drastically improve the management of very large inventory of site items, including handling the attributes and options in ubercart. We would put the beta together and submit it to the community.
If I am correct in theory this is a straight-forward project, the problem with Ubercart is the high-normalization of the tables with hard to follow relations. The simple answer is to create a master table (join, union, ...?) that pulls from the uc tables on download and updates them on upload. Somehowe the attributes and options need be delimited to one field in one record for every product (1 record per PK-SKU).
Nobody has tackled this, and to me it is common sense to do so. When I ran a large jewelry store site (www.forevermoissanite.com) - now down as the owner passed on, we just dl/ul'ed the inventory using one spreadsheet. This worked perfectly, and still seems the best way to me.
ANYWAY....looking for good php module person and others who would like to put a new module together and submit it. I think my visualized architecture is close to good, but don't have time to do it alone.