Currently, for the vanilla key, biome IDs are specified as the Bukkit enum value, or on other platforms namespaced IDs can be used as well. This is bad and should be deprecated, biome IDs should all be namespaced IDs.

How to do this

Currently, other platforms have Transformers to convert the Bukkit-style IDs to Identifiers, usually by just lowercasing it and slapping on minecraft:. This should be the other way around, on Bukkit, strip the namespace and convert the value to uppercase, then search in the evil Biome enum.

To prepare for this change, allow all platforms to use both evil IDs and namespaced IDs, then simply have transformers that print warnings when transforming evil IDs. Then, in 6.0, remove the evil ID transformers altogether.