I don't think prediction is a big deal especially on a utility based wallbreaker. I doubt we're going to have enough power to run through the whole tier with one/two moves. As a wallbreaker, if we're able to scare certain pokemon out, we can predict a switch and click a utility move. It won't be difficult to build a mon that doesn't have both the speed and power to 2hko the entire tier.I've seen a few comments about how we shouldn't choose STABs that have immunities. I disagree with that notion completely. 30i will probably already be the least prediction-reliant Pokemon in the entire metagame, no exaggeration. Tinted Lens, coupled with the fact that we're unable to hold a choice item and therefore not locked into the first move we click, means that making good predictions will be less relevant with this mon than perhaps any other mon that has existed.
I don't believe that giving our STABs at least one immunity is mandatory, but introducing a tiny bit of prediction to a mon that can otherwise click moves with complete impunity is not a dealbreaker by any stretch. As long as our STABs are not literally Normal/Fighting or Ground/Electric or whatever, we'll be fine.
Re: resists, fat mons like Corv and Pex have great defensive typings but are also able to switch into strong neutral moves because they are fat. Modest Kyurem with Icicle plate can't 2hko Corv with Freeze Dry. Icicle plate Tinted Lens Weavile doesn't 2hko Arghonaut with Axel. These are 2 of the best wallbreakers in the tier currently and they are incapable of 2hko-ing the most common fat mons in the tier with neutral hits. Now if Kyurem had Tinted Lens and predicted Corv to come in and clicked Draco instead, that's a different story, but that shows you can still include an element of prediction without making it a type with common immunities. Low acc, stat droppers, recoil moves, multi-hit moves, low pp moves, etc can all be punished, and those are just the damaging moves. You gotta be careful clicking Thunder Wave when the opponent's Ground is still alive.
Anyway, part of the reason Tinted Lens is cool is because it eases prediction. If a mon has access to 2 STABs of comparable power, but one of them has common immunities, why would it ever click the one with immunities except for SE hits? 4x resists are pretty rare except for Grass and Bug, so it's likely that the opponent is not gonna have a resist to the reliable STAB anyway, so not having any resists to 2 reliable STABs isn't really gonna make much of a difference. If you want to hit SE, you'll have to predict. I would personally not like to see the second STAB be used essentially as coverage, especially because of our cool item.
All the Rock-weak mons that don't run HDB are purely offensive, and they all run a Choice item instead. 30i doesn't have the luxury of a Choice item or HDB, and we need to provide utility and not just power. Even Kyurem and Weavile run boots most of the time. Blace has zero defensive merit, and Volk and Miasmaw barely exist in the meta.I hard, hard disagree with this notion. There are plenty of rocks weak breakers that are viable in the tier, namely Kyurem, Blacephalon, Volkraken, and Miasmaw.
Another concern with a Rock weakness is 30b. With a Rock weakness, 30b either has to be offensive, or be item-locked to HDB. Other than the aforementioned Choice users and Pelipper, there isn't a single rocks-weak pokemon on the CAP viability rankings that doesn't use HDB overwhelmingly more often than any other item. During the first ability stage, a whole slew of abilities was banned because of being item-dependent, not wanting both formes to be item locked and the ubiquity of Knock Off. I see parallels here.
Honestly though, above all, I just don't see the merits. I've personally argued that Tinted Lens eases the pressure on our typing offensively, so it makes sense to focus on securing a decent defensive typing. I don't see what we gain from being rocks weak, except using it as a weird balancing tool. I think we have far more to gain from not being rocks weak.