Hi, I'm not very old in ubers, but I would like to propose these changes plus a UR.
View attachment 192149C- to UR
This pokemon does not deserve to be viable, because its only "niche" is to be a dual screener with the field, but from there it is surpassed by almost all the fairies and most of the electricians, basically there is almost no reason to use Koko in ubers , so I recommend that you stay unranked.
View attachment 192170C+ to B
Yes, I know what they will be thinking "to use Chansey, if Blissey can have shed shell to escape gengar?", The reason is that it has a larger bulk than Blissey, apart from hitting with less power, count better to several pokemon, for example to primals or Xerneas.
calcs:
252+ SpA Kyogre Water Spout (150 BP) vs. 248 HP / 252+ SpD Eviolite Chansey in Rain: 210-247 (29.8 - 35.1%) - 18.7% chance to 3HKO
252+ SpA Kyogre Water Spout (150 BP) vs. 252 HP / 252+ SpD Blissey in Rain: 262-310 (36.6 - 43.4%) - guaranteed 3HKO
0 Atk Groudon-Primal Precipice Blades vs. 252 HP / 252+ Def Blissey: 393-463 (55 - 64.8%) - guaranteed 2HKO after Leftovers recovery
0 Atk Groudon-Primal Precipice Blades vs. 248 HP / 252+ Def Eviolite Chansey: 288-339 (40.9 - 48.2%) - guaranteed 3HKO
+2 252+ SpA Xerneas Focus Blast vs. 252 HP / 252+ SpD Eviolite Chansey: 270-318 (38.3 - 45.1%) - guaranteed 3HKO
+2 252+ SpA Xerneas Focus Blast vs. 252 HP / 252+ SpD Blissey: 338-398 (47.3 - 55.7%) - 78.5% chance to 2HKO
With this they realize that Chansey receives the blows better than Blissey, so for B.
View attachment 192174 C+ to B
Little more of the same as Chansey, I was surprised to see this pokemon in such a low rank, this pokemon is more than a niche, it works very well with Deoxys-A, basically it is as underrated as Chansey, it is a very good stallbreaker with terrain, unlike Koko it is possible to differentiate from others of its same type, so for B rank.
View attachment 192202C to D
Basically it is surpassed by Lunala, the only reason to use it on Lunala is its power, but Lunala puts a Calm Mind and voila, there are basically no reasons to use it on Lunala.
Now, the good:
View attachment 192182UR to C+ / B-
]The niche of this pokemon is doubtful, since it is surpassed by Arceus-Fairy, but nevertheless it has a niche and is to stop the special offensive dragons like Palkia or some Rayquaza, in addition to being semi offensive it can stop threats that Chansey and Blissey no, it's also like a combination of Chansey and Blissey with Arceus-Fairy, he has a wish like Chansey and Blissey, but with the type and offense of Arceus-Fairy, so I say it must be viable.
In what situations does Sylveon beat the uber fairies?
It has pixilate, which gives it a bit of extra power, it also has a slight but remarkably better confrontation against Mega Sableye, neither does it spend the Arceus space, being able to carry another arceus, and over Chansey and Blissey it has its obvious greater power and more Xerneas It has Wish and a special defense a little greater, this means that it has a better confrontation against Gengar, because Xerneas occupies power herb or another object, Arceus-Fairy cannot carry, Blissey can but is less powerful, so in conclusion Sylveon is unique the metagame, because there are no pokemon that do exactly the same as him, being an offensive Wisher, and of these there is none.
https://play.pokemonshowdown.com/battle-gen7ubers-966071698
View attachment 192201UR to C+
This pokemon has an inconsistent niche, since it is a pokemon with a low bulk, but with Unaware, which thanks to this has its niche in ubers, in addition to its low stats, it has a niche for the following.
In what situations does Clefable beat the uber fairies?
Well, against boosters such as: GeoXerneas, CM Kyogre, Arceus SD + Extreme Speed, etc ...
Well anyway, there are not many things to say about Clefable, basically it is a Cleric with Unaware and ready, nothing more to add.
https://play.pokemonshowdown.com/battle-gen7ubers-966077770
hope you like.