I might be misunderstanding your comment "There are no other reprints entered into the database", because I see a dozen different printings of the softcover. Could you clarify?
There's already an 8th printing in the database:http://www.comicbookdb.com/issue.php?ID=137315
But, to answer your question about entering an edition which has a different imprint than the original, after you've cloned the original and made the necessary adjustments and submitted the entry, you'll then have to edit the newly made entry and then change the imprint.
I would be surprised if DC began a separate series of printings for the Vertigo editions. Looking at the editions in the database already, I can see how they might prompt some confusion. The 8th printing from 2004 has the Vertigo imprint applied. The 10th printing doesn't have the Vertigo imprint applied and is dated 1990 currently. Not every edition has a cover uploaded yet. Some that do have covers uploaded clearly have the Vertigo logo on the cover artwork, but the imprint hasn't been applied to the entry. The inconsistent dates aren't necessarily the fault of the members who created the entries, because publishers don't always update the dates in their books for subsequent printings. And for even more confusion, some members will change existing entries and upload different cover artwork to reflect the one in their possession instead of creating a variant. This seems to occur with great frequency with popular titles that have seen many printings over the decades, and it will take a large group effort to make sense of some of them. Sorry, went off on a bit of a tangent there...
You shouldn't have to enter the 8th printing, because as I said, it's already present in the database. I'm not certain whether I've answered your questions or not, but I hope so.