On the subject of the Goldfish's nationality:
Goldy is not rough-hewn enough to be Arashi, too wooden to be Baronies. Anglean style is apparently giant blue squares, which this isn't. Chaladon has unnecessary flourishes, which the Goldfish does arguably have with its "fins", though they prefer very compact hull designs that reduce wood usage. Yesha has wooden construction for its hulls, but prefers multiple balloon sacs and metal incorporated into it, making their ships almost as rough as Arashi. It has a strong Mercantile touch to it due to extreme similarity in helm design to the Magnate and Mobula (helm in front of pavilion, no other faction has that), and the somewhat ornate "fins" and armor walls. The balloon style is most similar to Chaladon.
It most definitely is not Baronies or Arashi. Based on aesthetics it is most likely Chaladon or an odd example of Yeshan ships. Or Anglean because they don't have a Skirmish representative at all. It is possibly Mercantile due to extreme similarity in helm design to other Mercantile ships and overdecoration common to them.
Yeshans seem to prefer simple, effective firepower configurations with utility slots. Chaladon prefers maneuverability and speed at the cost of toughness and gun count, with reliance on side guns. Mercantile prefers withering frontal firepower from medium range and overlapping arcs at the cost of reactivity and speed. Durability is a little below average. Anglea prefers strange, vertical configurations, I guess.
So in terms of general firepower configuration, mobility, and toughness, it is most similar to Chaladon designs. There's a reliance on side guns, and the armor isn't very strong. In terms of Mercantile, Goldfishes can provide withering firepower with certain configurations, though Goldfishes prefer close-range. Arcs overlap somewhat but not very well due to use of a heavy gun. However, the Goldfish is tougher than Chaladon ships due to its hull, making its overall durability more average.
In terms of repair layout, the hull is in a well-monitored location, repair layout is flexible, with the engines being the greatest vulnerability. Mercantile ships have very inflexible repair layouts, hull vulnerability is a mixed bag, but engines are the greatest vulnerability in repairs. Chaladon has accessible hulls with flexible repair layouts, with engines being the greatest vulnerability. Yeshan engines are not extremely vulnerable in terms of repair, though they are vulnerable to disable.
So it shares the repair layout weaknesses and advantages of Chaladon ships most closely.
Overall, it is likely not a major, commissioned ship from any faction, making it more of a mercenary ship. It has aesthetic similarities to Mercantile and Chaladon ships, with handling properties of Chaladon ships. It was likely designed by someone who traveled between the Vastness and Chaladon. The repair layout is like a Chaladon ship, which is a hefty improvement over Mercantile ones. Armor toughness is similar to Chaladon ships and overall toughness similar to Mercantile. It has a low gun count like Chaladon ships but is more frontally focused like Mercantile ships. The fins add an artistic, personal flourish.
If I had to guess, it was made by some shipwright in the Vastness who was heavily influenced by Chaladon design, due to the Mercantile helm design, with a compromise of firepower styles and more Chaladon handling. It was likely designed for the shipwright's personal ship or commissioned as a pleasure ship for someone adventurous that became popular among private owners. The shipwright themselves was likely a traveler between the Vastness and Chaladon.
In other words, SS Mary Sue.
As for the Aces/Mercenaries question, definitely mercenaries. There's enough people out there playing Alliance that are definitely not aces. Definitely not.