Well, I have had a play.
Changing the contenttype for an epub is enough to get it displayed in the "News & Magazines" section. But, it is read just like any other epub.
So, I tried changing the extension to .kepub.epub. That worked as well. Opening it from the "News & Magazines" section and the reader app used was different to the normal kepub. But, the TOC and a few other things didn't work correctly.
The example database I have is from firmware 2.0.0 (I think). The database entries for the newspaper has hierarchical TOC entries. I could reproduce this, but the TOC rows created for a kepub book have changed in one of the recent firmware versions. There are extra rows for the TOC and I don't know how to handle them when turning it into a newspaper. I tried a couple of guesses, but they didn't work. And one of them caused my Glo to believe it didn't have any books on it.
That means there isn't much that can be done without knowing what Kobo now puts into the database. I'll second ichrispa's request for a copy of the database from a device that has at least one newspaper in it. And a copy of the actual newspaper file would be good. It will probably be encrypted and I won't be able to read it, but I should be able to glean the structure and compare it to the database. It doesn't matter if it comes from a Touch, a Glo or a Mini and any firmware version after 2.1.1 should be suitable. But a 2.3.1 or 2.3.2 would ideal.