Goabalt is a rather iffy Mon to use in Vega. While it does boast the same typing as Bisharp, it does not come near close to Bisharp's power in any way due to Bisharp having Defiant and Sucker Punch as priority. Instead, it is more of a Physical tank with great Attack stat. Unfortunately, it has 55 Speed, which is just below Tyranitar's Speed tier. Also, its typing offensively does get walled by Steel types unless if one runs Earthquake or Raging Flame. Defensively, while good, it gets demolished by Focus Miss, Flamethrower, and Raze Earth.
Overall, Goabalt is a decent choice as a Steel and Dark type attacker with pretty noticeable flaws in Vega.
In Procyon and Deneb however, Goabalt improved a lot due to the addition of Solid Rock, Assault Vest to make it incredibly tanky with Solid Rock, and the fact that Steel no longer resists Dark. However, the Cupricorn line is exclusive to Procyon.