How about implementing a master product table, where basic details of items could be centrally stored..?
Some multi vendor marketplace plugins already support this and it would be a very useful feature.
When adding a new listing, sellers could just search by certain attributes (for example UPC code, id, or partial product name) to query the master table and when having a match just have the attribute fields automatically populated, without always having to manually type in all the basic item info.
This would also enable the possibility for other features such as “Show other sellers selling this item” and price comparison.
A common feature is also to have a button for “I want to sell this too”, taking a seller from another seller’s listing to the already partially populated form for adding a new listing, again effectively copying the basic item data from the master table by querying with the unique id for this certain item.
Or, if not found in master table yet, copying the data from this another listing.
However, for every new listing added, the values in these certain fields could also be automatically added to the master product table, after admin/moderator review (possible to correct typos etc) and approval.
A thing to consider: Preventive measures should be taken so that search engines would not see copied listings as duplicate content.
Therefore probably only some custom fields should be copied in this manner, never the description and also preferably not the titles. All copied information should be editable before posting the listing, however fields like UPC code and id should probably be lockable from editing.
In my scenario, if there was a master product table in HivePress, I would then definitely also try to set up a sync from a certain external SQL database (another site I’m working on), since the needed basic info for these certain niche items would already be there for the most part.
Importing product data manually from a CSV or maybe JSON file should probably be the primary way to bulk add entries to the master table, but any automation possibilities for these would also be welcome.
And yes, the described feature would indeed be essential for many second-hand marketplaces too, not only for those selling new products, especially if dealing with niche collectibles and such.