I really think the AA should be a caster subclass, and I think as a user of devices that really fits the Artificer.

(I'd also like the fluff of the Artificer to be more explicit that it's not just about steampunk/*punk, but any form of magic item crafter, including someone like Celebrimbor or Faenor)

You could pretty easily reskin the Artillerist, with a few small changes, into being an Arcane Archer.

1. add weapon proficiency with all weapons that have the Ammunition property.
2. replace the 1st level spells with Ensnaring Strike and Hail of Thorns
3. replace one of the 2nd level spells with Cordon of Arrows
4. replace one of the 3rd level spells with Conjure Barrage
5. replace the 5th level spells with Conjure Volley and Swift Quiver
6. Reword (or provide a subclass exception) that all of the above spells can be used with Bows, Crossbows, or Firearms, or at least with the Arcane Firearm (ex: Swift Quiver excludes Firearms)
7. Explicitly call out that Eldritch Cannon can be a Ballista or Scorpion
8. Reword Arcane Firearm so that the sigils can be carved onto a ranged weapon that has the Ammunition property.  Casting ranged spells through this Arcane "Firearm" appears as though the Artillerist is "shooting" the spell at its target.  When you make attacks with this weapon, you can use your Intelligence Modifier for the attack and damage rolls, instead of Dexterity.
9. Maybe move Arcane "Firearm" to 3rd level, and Eldritch "Cannon" to 5th.

A more extensive revision into its own subclass, though, might have:

• 3rd level:
  • weapon proficiencies as above
  • Weapon Mastery with one Ammunition weapon
  • spell list and spell modifications as above
  • drop Eldritch Cannon entirely
  • move "Arcane Firearm" to 3rd level (with the above rewording) (needs a name other than "Firearm" though)
• 5th level: allow a Bonus Action attack with the Arcane "Firearm"
• 9th level: grant Extra Attack (with 1 cantrip substitution), but only with the Arcane "Firearm"
• 15th level: Bonus damage and Bonus range, with the Arcane "Firearm"