I will finally be able to specify custom types for scalar values. And I'm happy that the proposal is even more flexible.
The fact that this is done through the configuration file is, IMHO, a great idea, because it does not require to perform any modification to the schema file.
I'm +1 for this proposal. While there's been requests for something more comprehensive, I greatly appreciate the targeted scope of this proposal, which will allow us to make incremental progress for adopters.