I love the Vesta, and it is coming in season 7, it was confirmed by Dan Stahl.
Also I have a theory the Wells and Korath are not player ships, but NPCs in an upcoming mission involving the Tholians, in Season 7. Why else would it have its own unique weapon set as an NPC?
Remember, Tholians love to fuck when subsapce, and it has been known to cause time portals (In a Mirror Darkly)