Is there a way to have the default stock show 1? Everyone is at least selling 1 item and I am not sure the stock management would cause any issues. If someone is listing a product, then of course they have at least one to sell. It seems having having 1 listed as default would be safe. just a thought.
I downloaded the plugin WooCommerce Sold Individually and it set all my items in my store as individually sold items. Since that wasn't an option in my csv importer I would have had to manually change every listing. I'm not sure if that is what you are looking for but it worked great for me! 🙂