I'm moderately confident we'll see Eruption and / or Lava Plume as extra moves just for the burns.
Other than that, honestly even accounting for Infernal Parade, I don't think this'll be that difficult.
Thyplosion's middling attack stat means that even if they give it phisical coverage, being unstabbed will mean it will tickle.
If they don't give it phisical coverage, Blissey walls this for a year without even trying as supportive mon.
If they don't give it Focus Blast, Heatran also does, though I am assuming the offensive moveset is going to be Fire move / Infernal Parade / Focus Blast / probably a phisical coverage though could have Extrasensory i suppose.
I can see Sunny Day and/or Calm Mind as extra moves.
I don't think it'll be difficult, Thyplosion unfortunately for it just lacks a good special moveset ironically, and H-Thyplosion basically doesn't have an ability either (assuming they give it HA).
As for picks, honestly i'm looking at some of the spicy water types that can get away with eating Infernal Parade... Gastrodon might be good enough to work with it and either support with mud-slap or actually bonk the boss, both Vaporeon, Umbreon and Flareon have chonky special bulk to tank the damage and also go for a supportive set (Vaporeon also can run rain dance to disregard the burns).
Manaphy also could be pretty spicy, once more, Rain dance to shrug off the burns and reduce fire damage, if no rain dance it has Take Heart which is calm mind + refresh which serves same purpose while also boosting at same time.
What I'm also looking at is potential "anti calm-mind" options.
As far as Clear Smog users we don't exactly have a lot of options that aren't weak to either fire or ghost, basically just Gastrodon and Torkoal. Torkoal doesn't look like the best plan due to lack of recovery, Gastrodon on other hand would be my go-to choice (basically same set we used in the past, Clear Smog / Mud-Slap / Recover / Surf or Earth Power).
If we're looking at Snarl users, Arcanine and Umbreon are probably my best bets.
Acid Spray has a much wider distribution, the goodra suggested above looks like a good candidate but I also can see a few more.