@jasonsanjose, @gruehle and I chatted a little more about this and came up with the following:

1. Adding a `copy` method to the `FileSystem` API sounds good, but we should have a proper appshell implementation first. Although we *could* shim the implementation in JavaScript, platform-specific metadata wouldn't be preserved. Maybe @JeffryBooher or @bchintx can help flesh out the native copy implementations? 
2. It still seems like this feature should wait to land until it works similarly for files and folders, though @jadbox may have product management input on this.