Lots of negativity around the polymorphic JSON types. I don't think this will be a problem at all in practice. It's fairly simple to limit the conditional that

Lots of negativity around the polymorphic JSON types. I don't think this will be a problem at all in practice. It's fairly simple to limit the conditional that checks the type to exactly one place via a parsing step. This is basic OO - using factories to abstract conditionals. It will also mostly be handled by client libraries.