Couple of things jump out.
1. Being able to spend a bonus action to have your homonculus perform the Help action kinda steps on the Mastermind's toes a bit. But, it is pretty cool. And, it makes the pet VERY useful without needing to have a "combat pet".
2. I get the notion, but, a turret isn't really a pet is it?
3. Why does this class get extra attacks per round? I mean, the spell list for both subclasses is pretty robust - they've got damage spells down pat. None of the other casters get multiple attacks as a baseline. Seems a tad unnecessary to me. And, unless you pick up a magic weapon, doesn't that make the Enhanced Weapon infusion pretty much a must have? Additionally, I know that my current DM had a real issue with my forge priest getting a magic weapon at 1st level, I can't imagine he's going to be thrilled with someone who can create two magic weapons at 2nd level and give them to anyone.
4. I LOVE the fact that the artificer can swap out cantrips on a long rest. Very cool idea.
I want to see this in play. Fortunately, my group will be staring a new campaign very soon. Yay.