Araquanid checks in.
It's a water type, with extra resistance to fire, which your team needs. At the same time it diminishes your Steel weakness.
It's good as a supportive pokemon and your bulky offensive team needs support.
It's also physical, but I don't know what set you want your Kommo-O to have, so I'm just guessing special.
Now, going with my assumption that Kommo-O is special, it can learn flamethrower and there's your Fire coverage.
At the same time I believe Lycanroc can also learn Fire Fang if you ever need that.
So I noticed you have a Ground weakness which I'd rather alleviate with Dhelmise
Since you want Alolan pokemon, I think this one fits pretty nicely.
It's ability in steelworker allows for some random Anchor Shot, so have that just in case you meet Fairies and Muk isn't ready to battle 'em
It also has quite good defenses and the ability to retaliate with grass type attacks so there's that.
There you go. Another 2 bulky mons for your roster, filling in the 6 pokemon squad. Usually you'd want to have more on-rotation, but this should be a great base team.