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Freeze-Dry would be huge; something like Seismitoad would go from being neutral to Ice to becoming 4x weak.
To put it another way, Modest Mega Glalie Freeze-Dry 2HKOs 252/252+ Mantine, and that's a guaranteed OHKO with SR. The only real Water-type that sees real use and won't be 2HKO'd is...
Speaking of Grasses, what of Tropius? Fellow Harvest user, acceptable (though not amazing) offensive movepool, and unlike Exeggutor, SitrusHarvest doesn't get wrecked by Toxic Spikes. I'd say it'd be C- or D at the very worst, not unmentioned.
I'm not sure how Megahorn is 'way more powerful' compared to Return - the difference is only 16 BP, which, while not insignificant, isn't incredibly drastic when you take into account Feraligatr's better physical abilities. Especially since you're almost always using it as a neutral option...
Umbreon is the least interesting personally. It loses its Fighting, Bug and Fairy weaknesses but gains a weakness to Ground. Its movesets likely won't change that much and I'm not sure how much niche it'll have even with the new typing.
All three remaining Theorymons are interesting. MegaAggron...
There are so many amazing things about this fight (I just about lost it at Pound Sceptile), but I think my favourite part is how he keeps switching Donphan out everytime it gets Taunted, as if he's afraid it's some cancerous status. But only on Donphan.
I wouldn't run HP Fire on Protean Starmie even in Sun - a neutral STAB Thunderbolt/Ice Beam has the exact same BP. I'd probably run HP Ground if anything.
Not that both would get in unless one of them places second and gets a chance to be re-voted in.
After looking over some calcs, Torterra does seem like a pretty cool pivot, and a physically defensive spread seems like it can do quite a lot. Talonflame is just going to murder the poor thing with auto-Sun, but that's what you have five other Pokemon for I suppose. As long as the rest of your...
One possible drawback I could see to Protean Starmie is that most of its type conversions are pretty unfavourable defensively - Normal, Ice and Psychic are pretty bad in particular.
Still, great coverage and speed, only really lacking a switching move. Thunderbolt also immunizes it from...
I don't see Sceptile doing too much right now, except as a Dragon-killer or to mop up late game. It just doesn't hit hard enough on the special side even with Life Orb and it doesn't have Calm Mind/Nasty Plot, and coupled with being quite frail. It gets Swords Dance and could make use of a...
Cloyster and Blissey feel like they won't have too much room for creative discussion - Blissey would almost always be running Scald since there's little downside to running it over another move unless she's up against something with Water Absorb, and even then Toxic usually solves that problem...
Magic Guard Froslass
Immunity to SR on an Ice Pokemon? Fantastic. A 50% chance to OHKO offensive Dragonite through Multiscale with Life Orb with no penalty? Also great.