There's also Magic Bouncers, like Mega Absol, which resists Mach Punch and vaporizes it with Knock Off or Sucker Punch. Mega Absol is actually pretty decent in Inverse, as its Sucker Punch sweep can threaten entire teams. It only needs coverage for Ghosts and Psychic types -which Superpower handles right there, as most of those have poor Defense in addition to being Fighting weak. This frees it up to either run both Knock Off and Sucker Punch alongside Swords Dance or to fit in some utility move (Taunt, for instance) instead of running two Dark attacks.
I don't think Breloom belongs in S, though. Definitely A+, it does so many useful things like OHKO Mega Beedrill with Mach Punch, but Spore's relevance against offense teams is fairly low and stall can easily mitigate it by carrying both Hippowdon and Avalugg -whichever one gets Spored, the other switches in and Roar/Whirlwinds out or KOs with Earthquake Breloom, and honestly having both is good practice on any strongly stall-oriented team since there's not that many viable walls in Inverse in the first place and they're complimentary.
252 Atk Technician Breloom Bullet Seed (3 hits) vs. 0 HP / 0 Def Mega Absol: 279-327 (102.9 - 120.6%) -- guaranteed OHKO
It's certainly not switching in risk-free, though, and one mispredict means it's dead. The only other viable Bouncer is Espeon and I'm not even going to bother calc'ing that. (Btw, it probably wants to run Ice Beam for breaking Chanslugg + P2: Koff, Spunch, Ice Beam, SD|Play Rough|Superpower|ZHB sounds like the best set.) Mega Absol is also incredibly uncommon - it has a raw count of a whopping
9 on the most recent usage stats, compared to Avalugg's 422. (Though obviously this has no impact on its viability - you're right that's it's pretty good.)
Spore is certainly
less good against more offensively inclined teams, but Mach Punch is very very useful here. A Focus Sash set puts in a lot of work in my experience. From my experience, full stall itself isn't great at all (every good team needs some sort of stallbreaker to deal with Chanslugg+P2, and most stall teams are 6-0'd by Meloetta + Toxic Spikes support).
Balance is the most common playstyle, which is where Breloom shines - it's a lot easier to bring it in and fire off an attack or a Spore.
I think if anything, Loom should stay out of S because Miltank is a guaranteed counter which is plenty viable, and outside of Spore, Mamo switches in fairly well - it's not at the "I need a dedicated counter to this mon or I lose" level.
Haven't seen it enough to say. I think its Speed tier is too problematic for it to go in S, though, especially since it also hates the Normal spam of the meta. Breloom vaporizes it with Mach Punch, for that matter.
0 SpA
Porygon2 Tri Attack vs. 0 HP / 0 SpD Hoopa Unbound: 72-85 (23.9 - 28.2%) -- 93.9% chance to 4HKO
252 SpA Choice Specs Adaptability
Porygon-Z Tri Attack vs. 0 HP / 0 SpD Hoopa Unbound: 214-254 (71 - 84.3%) -- guaranteed 2HKO (note one is P2 and one is P-Z)
Saying it hates the Normal spam is misleading, since a) it only really hates stronger physical attacks, b) it's not supposed to switch in on strong attacks anyway, it's meant to come in on a free switch, and c) Normal spam is actually a lot less prevalent than you would think from the VR and from theorymon*. A set of Dark Pulse/Psy[chic/shock]/Knock Off/Filler 2HKOs the entire metagame, with or without rocks (again, Gengar aside, but who wants to switch in Gengar like that? It also needs to run Psychic itself to KO, and hope Hoopa doesn't run any kind of coverage). Its speed tier is actually fairly good for this meta - other than the lightning-fast mons such as Bees, a large number of mons sit around the base 70 Speed tier, or don't run as much speed. Notably, Hoopa can OHKO Meloetta with Psyshock/ZHB while outspeeding
most variants - something very few mons can claim. It also counterleads Bees by outspeeding non-mega and OHKO'ing through Protect with uninvested Hyperspace Fury which is cute. As for Breloom vaporising it:
252 Atk Life Orb Technician Breloom Mach Punch vs. 0 HP / 0 Def Hoopa Unbound: 192-227 (63.7 - 75.4%) -- guaranteed 2HKO
So you can't just bring Breloom in to revenge it unless it's taken a fair bit of chip damage (which means it's probably gotten at least 2 attacks off, so you've lost at least one team member). All in all, it's completely nuts.
Its advantage is that it's a win condition. Physically Defensive with Calm Mind can sweep the meta on Psyshock alone, so any team fool enough to carry no phazing and no Toxic is in serious trouble. It can be broken through by powerful Fighting type attackers as well, but that's actually about it outside of the Toxic and phazing points. (Inverse does Cresselia huge favors overall, with Knock Off being resisted and U-Turn being resisted as well) Meloetta hits harder and is a whole 5 points faster, but it's considerably less bulky. Admittedly the Normal typing makes it less vulnerable to Fighting type attackers, but it's still a lot easier to break Meloetta by attacking it.
Cresselia is one of the best win conditions in the entire meta -Toxic is often forgone entirely by teams because dropping it is such a small cost, and if you can clear out whatever powerful Fighting attackers the enemy has, at that point Cresselia can often sweep teams by itself as a result.
I can see some of your points, but it's not really getting a good chance to set up on more offensive teams. It does
I actually find that Toxic is
more common on my teams - I used to slap it on half my physical attackers to lure Avalugg (since they can't break it otherwise). I don't know what you mean by "dropping it is such a small cost" - it's integral in breaking bulky cores which wall most unboosted things otherwise. It also hates Trick a lot more than Melo does.
Ursaring is an amazing stallbreaker, definitely.
252+ Atk Guts Ursaring Facade (140 BP) vs. 248 HP / 252+ Def Avalugg: 174-205 (44.2 - 52.1%) -- guaranteed 3HKO after Leftovers recovery
However, it can't break Leftovers Avalugg unless the item has been removed or it goes for the Swords Dance. I don't think full stall is really a thing in Inverse either, anyway, as in practice you just don't have enough stallmons. In my experience stall teams in Inverse tend to have a powerful defensive core (Chansey/Avalugg/Hippowdon is my preferred one) and then the other half of the team is more oriented toward attacking things.
I can see B, though, definitely.
Or if Avalugg has taken a small amount of chip damage from spikes support (I ran Ursaring on spike stack offense):
252+ Atk Guts Ursaring Facade (140 BP) vs. 252 HP / 252+ Def Avalugg: 174-205 (44.1 - 52%) -- 75.8% chance to 2HKO after 1 layer of Spikes and Leftovers recovery
Or switching in to another attack:
252 Atk Adaptability Mega Beedrill U-turn vs. 248 HP / 252+ Def Avalugg: 78-94 (19.8 - 23.9%) -- possible 6HKO after Leftovers recovery
which leaves it down to a roll.
Full stall isn't really a thing though, no.
* I personally think normalspam isn't common because while it's unresisted, you need SE hits to break stuff like avalugg on the physical side, so normal just doesn't cut it. There's also a notable lack of legal, good, Normal-type hard-hitters - you're limited to Raptor/PZ/Lop for fast mons, and Ursaring for a slow monster.