Vista class ships, Admiral Akaar and President Bacco are either in STO, will be in STO, or have been mentioned in STO. Yet Sisko is still with the Prophets. Janway is still alive. Risa, the Klingon Great Hall (and presumably Pluto) haven't been blown up and the Borg (the most over used villain in Star Trek) haven't been put out of their misery yet.
Cryptic really is picking and choosing what elements of Soft Canon they are using. I wonder if Ezri Dax was ever in command of the Aventine, or if it has a better Slipstream drive than other ships.
Anyway I think it should be a science-cruiser hybrid, maybe with some elements of an escort, either tier 5 or 6.
However the devs implement the Vesta class, I guarantee that it will only bear the vaguest resemblance to what it is in the novels. As the ship was written, it would be really overpowered in STO.
That's why I think that maybe, it could be a tier 6 or higher, whenever Cryptic gives us the Fleet Admiral, President of the UFP or Galactic god ranks (or whatever they decide to name the ranks higher than VA). Although I don't really want a 6th tier of ships if I have to give up my Defiant refit or Sovereign ships to keep up.
Mark Rademaker, the creator of the Vesta, stated it would be a Science Ship with a Tactical edge, like the Luna in-game.
Also the Luna has cannon capability so that should be reflected in-game as a unique trait.
The Luna/Recon Science Vessel can't use dual cannons, if that's what you mean. Every ship can use regular cannons.
I would have guessed it might be a Star Cruiser. If you say it's more a Science Vessel with a more tactical focus, I suppose we could do what some people proposed (inapporitately IMO) for the new Vulcan ship.