I think that it would be helpful to have better interoperability between Swift and JavaScript. There are a lot of useful packages on NPM that don't have equivalents for Swift. It would be helpful if Apple provided easier ways to use NPM packages in a Swift project. Currently, the JavaScriptCore framework is missing many standard things used in many packages, like the fetch API. It would be helpful to be able to run sandboxed JavaScript code inside of a Swift app but allow access to specific domains, folders, etc., using a permissions system similar to Deno.
JavaScript/Swift Interoperability
If you have a suggestion, you should raise it at: https://feedbackassistant.apple.com/
When doing so, I recommend you list the specific APIs you want, and the justification for them. A suggestion that Apple just implement some of the missing APIs won't get very far.