What are some crummy Pokémon you wish for a little more valuable to use outside of a single player campaign and how would you make them better for competitive? I'll start

>Castform's Forecast now activates if you are holding a weather rock
>Gives an automatic +1 SpAtt boost upon transforming
>All of its weather forms get a Rotom-Appliance style boost, gaining 15 points in HP, Def, SpAtt, and SpDef (not as huge a jump as Rotom got, but enough)
>Gains access to a ton more moves, but namely Aurora Veil, Life Dew, Morning Sun, Heat Wave, Dazzling Gleam, Terrain Pulse, Destiny Bond, and Misty Explosion. Tailwind, Defog and Icy Wind become level up moves instead of tutor moves
>Maybe gains a Rock type Sandy form as well, which would then give it access to different sandstorm related moves

Now it can be a weather setter for any weather and has the capability of actually staying out once the weather is set. The Rainy and Sunny forms become reliable offensive pivots with some versatile coverage while Icy becomes way bulkier and a great support mon being able to set up snow, dual screens, tailwind, and then attack all in one kit.