The Borg Queen origin story is the one I'd most have liked to see, actually.
Memory Alpha wrote:
Judith and Garfield Reeves-Stevens pitched a story with Alice Krige as a Starfleet medical technician who makes contact with the Borg from Season 2's (" Regeneration") and becomes the Borg Queen.
It would have explained her obsession with humanity and wanting a human equal.
Here are brief synopsis the rest of ENT's unmade episodes:
Here's a script review of Star Trek: The Beginning
, the unmade Romulan War film (where Enterprise is at Risa and misses the whole thing): http://www.aintitcool.com/node/34635