bit rusty on the competitive scene and it's been a while since i've done anything with CAP so bear with me
a) What are some attacks that we should not be weak to?
This question has pretty much fully been hashed out by now, but I'll throw in my thoughts on some of the most standout examples.
Scald is
the big one, of course, being ubiquitous on the most domineering pivots such as the SlowTwins and Toxapex, as well as a number of other bulky water types that personify the archetype. While it has been noted that we may be able to get away with merely a neutrality against Water given the low power of most Scald users, I do believe that a resistance is still preferable given the SlowTwins' relatively competent Special Attack; minimizing the amount of chip our primary targets can do in the typing phase will allow us to prioritize overcoming their bulk later on in the process. Toxic poses a similar issue, being incredibly prevalent on major pivots such as the aforementioned Pex, Blissey (itself one of our main targets as a Porter) and Amoonguss as a dangerous source of chip. I don't think there's much argument that having some way of fighting off Toxic, whether through type immunity or otherwise, will be vital to ensuring CAP28 can maintain pressure against bulky pivots.
On the other hand, I don't feel as though the main Pivot moves are worth tailoring our typing to beyond ensuring neutrality against them if we can manage it. U-Turn is a true example of a low-power move, primarily used by
more passive pivots such as Mandibuzz and Corviknight without even STAB or burn chip to back it up as Scald's primary users have; while there are some exceptions to this, such as Dragapult, Rillaboom, and Syclant, these mons can already be pressured through other means compared to the SlowTwins due to their low bulk, and shouldn't be our top priority. Volt Switch is more problematic, since its main users (Zeraora, the Rotoms, Krillowatt, Magnezone) actually have the power to make it hurt. That said, I believe that tailoring CAP28's type to it would actually be to its detriment; the obvious choice of Ground-type to block Volt Switch, for example, would ultimately leave us more vulnerable to the bulky waters that we should be focused on, while still doing little to dissuade Rotom-W and Krill in particular.
Lastly, I think
Close Combat is indeed worth looking out for given its prominence on common pivot partners such as Zeraora and Urshifu; being unable to handle its power will ultimately force CAP28 to be able to take out the pivots as soon as possible in order to fulfill its purpose, but a resistance against it would likely allow for more consistent pressure, forcing the pivots to think twice about bringing in Zera or Urshifu against us.
b) What are some Pivots where having a super-effective STAB will likely matter?
The
SlowTwins are, of course, enemy number one, boasting the perfect storm of Teleport, good mixed bulk, and Regenerator to become truly difficult to crack; while Blissey and Chansey, the other premier Teleporter, have more lopsided defenses (even with Chansey's Eviolite) that are relatively easy to exploit without the need for a super-effective STAB, the same can't be said of these two. Furthermore, their distinct defensive differences makes pressuring both -- a critically important matter, lest one simply replace the other when CAP28 is complete -- somewhat of a challenge; type advantage thus serves as an effective catch-all against both.
Besides these two, Regenerator pivots command perhaps the most attention, and of this group
Toxapex is definitely the most egregious; every advantage counts if we want even a chance of beating its frankly obscene longevity. As perhaps the ultimate example of a passive Pokemon in the current meta (save for maybe Blissey), I believe that Pex should be our top priority to beat after the SlowTwins; if we can conquer it, that will be a strong indicator towards CAP28's success as a Roadblock. Other noteworthy Regenerators to consider are
Tangrowth,
Amoonguss and
Astrolotl, but I feel that these mons are secondary to Pex with their greater degree of vulnerabilities in mind. Additionally, while not Regenerators themselves, bulky Flying types such as
Mandibuzz and
Tomohawk (and the somewhat less prevalent
Corviknight) boast similar longevity that a super-effective STAB would aid greatly against.
As an alternative route, CAP28 may benefit from having advantage against
Zeraora (and
Urshifu, though he's not a pivot in his own right); pivoting is a two-part system, after all, and a lot of the strength of the strategy lies in the threats that it can bring in, with these two being the most prevalent. As mentioned previously, being able to pressure Zeraora, Urshifu, and other common pivot partners would serve as a method of pressuring pivots as a whole, limiting their ability (the Porters in particular) to bring in their team's offense without consequence.
c) With respect to the Concept Assessment Final Post are there any typings that are relevant to the roles / playstyles mentioned?
Firstly, I'd like to posit
Electric as perhaps our best choice for an offensive typing, checking off many of our boxes with the sheer coverage it offers against pivots. Electric alone offers vital offensive pressure against the bulky Water type pivots such as the SlowTwins and Pex, as well as the previously discussed Flying pivots; as a bonus, it also grants a resistance to Volt Switch and Plasma Fists from Zeraora and an immunity to the Stun Spore occasionally carried on Amoonguss and Tangrowth, giving it a slight degree of defensive utility, and while Parabolic Charge is far from an ideal draining move, it isn't necessarily useless considering the amount of pivots it can hit for super-effective STAB against.
Grass has some similar advantages on this front -- albeit more defensively-oriented ones -- with its most notable distinctions being its resistance to Scald, superior draining options, and immunity to Amoonguss and Tangrowth's sleep-inducing moves; that said, considering the loss of coverage against key targets like Toxapex and the Flying types and the greater degree of weaknesses Grass has, I believe that Electric should take priority if we are to choose one or the other.
From a strictly defensive perspective,
Steel is as always a potent option for its Toxic immunity and general chip resistance alone; the resistance to the SlowTwins' Future Sight and Libra's Doom Desire that it offers is a nice perk as well. That said, its neutrality against Scald and weakness to Close Combat may be problematic without a secondary typing that alleviates these issues.
Dragon has also been brought up, and it's certainly worth considering: resistances against Water, Electric and Grass automatically enable it to hinder the notable pivots of these respective typings, and access to a STAB phazing move that, unlike Circle Throw, isn't resisted by practically every pivot on the block gives it a major niche by default.
Besides these, there are of course the other options with immunities, such as
Dark, Ground, and
Flying, as well as
Poison with its particular immunity to Toxic. In Dark's case, STAB Sucker Punch offers the opportunity of shutting down fast VoltTurners such as Zeraora and Dragapult after the pivot brings them in, but the type's true strengths lie in its immunity to Future Sight and access to STAB Knock Off, which can offer a greater degree of more consistent offensive pressure and cripple the effectiveness of both pivots (especially the SlowTwins and HDB-reliant pivots) and their partners. Ground, as discussed, offers an immunity to Volt Switch and super-effective STAB against Pex, but otherwise is a detriment against the bulky Water and Grass pivots and has no real value against the Flying pivots. Flying offers super-effective STAB against the Grass pivots and a resistance to U-Turn, but its weakness to Volt Switch is debilitating and its Ground immunity doesn't have much bearing against the targets we're trying to punish, while Poison offers its aforementioned Toxic immunity and U-Turn resistance in exchange for a dangerous weakness to Psychic and little offensive pressure to speak of. If we are to use immunities at all, I would frankly recommend
Dark or, as a more niche pick,
Ghost: immunities to Normal and Fighting leave Chansey and Blissey helpless short of Toxic while also walling Close Combat and Tomohawk's Aura Sphere (though it is vulnerable to being wiped out by Urshifu). Beyond that, it also boasts super-effective STAB against the SlowTwins and resists U-Turn, while also having some interesting move options that can be catered to such as Shadow Sneak for priority and Poltergeist to fish for items. That said, Knock Off is definitely something to be wary of if we go down that route.
I apologize for the length of this post, but I had quite a lot to remark upon! This is a very interesting concept that's highly relevant in the current meta, and I'd like to see it realized to its fullest potential.
