Honko
he of many honks
I don't think it makes sense to separately tier the forme changes that are volatile and reversible (stuff like Aegislash, Meloetta, and Castform). Outside of the aesthetic changes (which I think we all agree should be irrelevant to tiering), I don't see much conceptual difference between these forme changes and the effects of regular stat-changing and type-changing moves that many Pokemon without alternate formes can use.
Some scenarios to illustrate what I mean:
A) Aegislash uses Shadow Ball, increasing its offensive stats and decreasing its defensive stats. It can use King's Shield to revert the changes. If it switches out, the changes are lost and it must use Shadow Ball again to get them back.
B) Omastar uses Shell Smash, increasing its offensive stats and decreasing its defensive stats. It can use Haze to revert the changes. If it switches out, the changes are lost and it must use Shell Smash again to get them back.
A) Castform uses Rain Dance, changing its type to Water. If it switches out and then comes back in 10 turns later, the changes are lost and it must use Rain Dance again to get them back.
B) Starmie uses Camoflauge, changing its type to Normal. If it switches out and then comes back in 10 turns later, the changes are lost and it must use Camoflauge again to get them back.
A) Meloetta uses Relic Song, changing both its stats and typing. If it switches out, the changes are lost and it must use Relic Song again to get them back.
B) Ditto uses Transform against a Meloetta, changing both its stats and typing. If it switches out, the changes are lost and it must use Transform again to get them back.
C) In Gen VII, GameFreak changes Geomancy to also give the user Fairy/Ground typing. Smeargle uses Geomancy, changing both its stats and typing. If it switches out, the changes are lost and it must use Geomancy again to get them back.
I propose that a forme change only be tiered separately if it involves a stat and/or typing change AND it is non-volatile, by which I mean if the Pokemon switches out while in a particular forme, it will ALWAYS remain in that forme when it switches back in, regardless of weather or other external field conditions.
Aegislash, Meloetta, and Castform would each be tiered as a single Pokemon because their forme changes can be reverted by switching out or external field conditions changing. Megas, primals, Shaymin, and Darmanitan would have their formes tiered separately, because they always switch in as whatever forme they last switched out as.
Some scenarios to illustrate what I mean:
A) Aegislash uses Shadow Ball, increasing its offensive stats and decreasing its defensive stats. It can use King's Shield to revert the changes. If it switches out, the changes are lost and it must use Shadow Ball again to get them back.
B) Omastar uses Shell Smash, increasing its offensive stats and decreasing its defensive stats. It can use Haze to revert the changes. If it switches out, the changes are lost and it must use Shell Smash again to get them back.
A) Castform uses Rain Dance, changing its type to Water. If it switches out and then comes back in 10 turns later, the changes are lost and it must use Rain Dance again to get them back.
B) Starmie uses Camoflauge, changing its type to Normal. If it switches out and then comes back in 10 turns later, the changes are lost and it must use Camoflauge again to get them back.
A) Meloetta uses Relic Song, changing both its stats and typing. If it switches out, the changes are lost and it must use Relic Song again to get them back.
B) Ditto uses Transform against a Meloetta, changing both its stats and typing. If it switches out, the changes are lost and it must use Transform again to get them back.
C) In Gen VII, GameFreak changes Geomancy to also give the user Fairy/Ground typing. Smeargle uses Geomancy, changing both its stats and typing. If it switches out, the changes are lost and it must use Geomancy again to get them back.
I propose that a forme change only be tiered separately if it involves a stat and/or typing change AND it is non-volatile, by which I mean if the Pokemon switches out while in a particular forme, it will ALWAYS remain in that forme when it switches back in, regardless of weather or other external field conditions.
Aegislash, Meloetta, and Castform would each be tiered as a single Pokemon because their forme changes can be reverted by switching out or external field conditions changing. Megas, primals, Shaymin, and Darmanitan would have their formes tiered separately, because they always switch in as whatever forme they last switched out as.