littledan: I think there is precedence for [[Prototype]] override in webidl:

https://console.spec.whatwg.org/#namespacedef-console

For historical web-compatibility reasons, the namespace object for console must have as its [[Prototype]] an empty object, created as if by ObjectCreate(%ObjectPrototype%), instead of %ObjectPrototype%.

And WebIDL allows this:

https://webidl.spec.whatwg.org/#ecmascript-binding

Unless otherwise specified, the [[Prototype]] internal slot of objects defined in this section is %Object.prototype%.