@Arios: Oh sorry. I misunderstood you.
I thought the trick was to make the reader to start at the cover page WITHOUT showing a TOC entry. My bad, I have too imagination...
Then, I don't know for other e-readers, but on the Glo, simply adding a line on the ncx works, as I explained on my previous post.
I'll try to make a script of something to automatize it. When adding a ebook to Calibre should be the perfect moment. I hope it is doable. I'm still discovering it.
Thank you for your help