I came up with an Arcanine build for the people in Scarlet which can work as an attacker or support (probably, haven't tested supporting yet).
(Also kinda because I couldn't be bothered to look for an Iron Moth in area zero)

Arcanine @ Shell Bell
Ability: Justified
Tera Type: Fire
EVs: 252 HP / 252 Atk / 4 SpD
Adamant Nature
- Temper Flare
- Helping Hand/Sunny Day
- Howl
- Morning Sun
Flare Blitz is your main attacking move, even though it has recoil, simply because Temper Flare was too weak. Howl helps you raise your attack alongside Justified, which is essentially like using SD if Wo-Chien spams Snarl/Dark Pulse. Morning Sun is there just in case. Helping Hand or Sunny Day allows you to play a more supporting role as well (Sunny day boosts fire attacks, plus Morning Sun heals more).
Solo Attempt 1:
Ended up just barely timing out with like, 5% HP left. Got a little unlucky with the AI not using Dark moves enough, and also dodging a Snarl once, forcing me to use 1 more turn to set up. Overall, fairly optimistic for attempt 2.
Solo Attempt 2:
This was the one, I managed to beat this one by getting a little more lucky. More Dark moves into me, and got Drifblim and Staraptor as partners, which helped chip the slug down while the shield wasn't up. In fact, Staraptor was actually the one who killed Wo-Chien by stealing my kill and moving first, which was pretty disappointing. Arcanine is fairly slow to win as a build, wouldn't recommend for solo unless you don't just wanna use Moth.
I haven't tried this build as support yet because my NSO subscription ran out, but I'll edit this post whenever I do. On paper, it would work. I'm fairly confident that it could work in practice as well.