When creating custom biomes, I think it would be cool to have the ability to have the climate cycle within that biome. You would be able to set Temperature, Downfall, and Snow Accumulation on a cycle. The cycle would be tied to the in game tick counter, so using the /time add command, or setting random tick speed to a higher value would speed up the cycle. This would be very useful if you want your custom biomes to have a seasonal cycle, you could also do the same for existing biomes if you wish.
Here is an example of a custom biome with a climate cycle
Duration: 72,000 (ticks)
Duration: 70,000 (ticks)
The cycle would be gradual, so the temperatures would not just abruptly change, they would gradually change. The tick value under each cycle would be how long it takes until the climate of the next module is met, add the tick value of all modules added together would be the full cycle.