Exeggutor and Persian yes.
Alola Exeggutor is weak to Bug, Poison, ICE, Dragon, Fairy, and Flying. Kanto Exeggutor is weak to BUG, Dark, Flying, Fire, Flying, Ghost, Ice. So Alola form loses weaknesses to Dark and Fire (which are extremely common) as well as a 4x weakness to bug moves such as u-turn, but gains weaknesses to Dragon, Fairy, and a double weakness to Ice. It isn't much of an improvement, since he also loses some resistances (but gains several 4x resistances) but an improvement nonetheless. Though the loss of Harvest and/or Chlorophyll will also hurt it. Overall, the improvement is there, but not by much to be quite honest.
Pretty much agreed, but I think stats will determine whether it is slightly better or actually slightly worse. Dragons tend to do well in the stat department though.
Alola Persian is weak to Fighting, Bug, and Fairy. Kanto Persian is weak to Fighting. So it gains two weaknesses, however, the Dark typing is a really good typing (especially since it now gets STAB Knock Off), and it has two of the best abilities in Fur Coat and Technician, with the former increasing its defensive bulk far beyond that of its Kanto counterpart. Overall, an improvement, in both offense and defense.
Bear in mind we cannot assume they keep Kanto stats. Furfrou has "bad" Defense to make up for having Fur Coat, but that "bad" Defense is 60, the same as regular Persian's base... This does make me hopeful they wouldn't feel a need to reduce it further, but you never know.
I also think Alola Muk will be an improvement. We don't know its stats, but Poison/Dark is superior to mono Poison. Poison/Dark grants it an immunity to psychic, a weakness of poison, making it only weak to ground type moves. This helps Alola Muk a lot on the defensive side, and dark is a very good offensive typing. So overall increase in defensive and offensive potential.
Agreed.
Alola Sandshrew is def not an improvement. Gaining two 4 times weaknesses is not good, and being slower on top of all that, not good at all. Good offensive potential, but overall the mono ground kanto form is probably better.
I say again, two STAB priority moves are possible, and even if not, there is Trick Room. Don't count A-Sandslash out yet.
Alola Ninetails is not an improvement. Ice is a powerful offensive typing, but terrible defensively. Fire is also strong offensively, and bad, but not terrible, defensively. A slight dip from its Kanto counterpart.
A-Ninetales is Ice/Fairy, not Ice/Fire. Fairy is one of the best defensive types in the game. I think you need to rethink this prediction.
Alola Raichu is probably not an improvement. Adding the psychic typing is good offensively, but defensively, it now gains weaknesses to Bug (U-turn), Ghost (Shadow Ball, Shadow Sneak), and Dark (Knock Off, Sucker Punch) on top of a weakness to Ground. Those are bad weaknesses to have, as opposed to Kanto Raichu which is weak to only Ground.
Whether gaining weaknesses actually matters depends on whether Alolan Raichu functions as a sweeper. See Weavile for why having every weakness under the sun doesn't matter when you have crazy STAB coverage and the stats to OHKO.
Alola Raticate is a tough one. While it gains better offense with the Dark typing addition, it also gains weaknesses to Fairy, and a 4x weakness to Fighting. Alola Raticate better look out for Mach Punchs (not that it could survive them before). Its abilities didn't give it anything over its Kanto counterpart, so overall, it probably will be weaker, though STAB Sucker Punch will be useful and give it a niche.
Its abilities do give it a lot over its counterpart. People overlook Hustle way too much. Plus Gluttony could be very useful if it gains a lot of HP. A-Raticate is almost undeniably better than regular Raticate, but it will probably still be bad.
Alola Marowak went from being weak to Grass, Ice, and Water to being weak to Dark, Ghost, Ground, Rock, and Water. While it has good offenses, and may form itself a niche, being weak to sucker punch/knock off, shadow sneak, earthquake, scald, and stealth rock is going to be killer for it, weakening it from its Kanto counterpart. And its abilities didn't make up for that.
Chandelure manages just fine, so I don't believe this doom and gloom on the defensive front. You also ignore the fact that it has three immunities. Will o Wisp makes up for Physical weakness somewhat, and it's very possible that priority will get a big nerf this gen because of abilities like Dazzling and Queenly Majesty, and moves like Psychic Terrain. Some of the Alola forms will really benefit from gaining STAB priority, but A-Marowak will very much appreciate if this new counter-priority meta comes true.
My thoughts.