- Evolve Castform
- Get rid of Forecast ability
- Give him all 4 Weather-setting abilities and just have him change form with the weather innately without an ability (some mons already do this)
- Give all 4 forms different stat spreads that suit a certain playstyle
- Make the sandstorm form Rock instead of Ground so it can take advantage of the Sp. Def. boost
I would say also make it half Flying Type but my instinct tells me the additional weaknesses would cripple the poor thing