EDIT: Proposal update in next comment.

The resolveId() method of the plugin model exposes the importee and importer path strings.
If an importNames variable was also exposed, it would expand the possibilities of plugins using the method.

// importNames examples
resolveId (importee, importer, importNames) {
  // Default import
  // import SomeModule from "SomeModule";
  importNames === "SomeModule";
  // Named imports
  // import { SubModuleA, SubModuleB } from "SomeModule";
  importNames === [ "SubModuleA", "SubModuleB" ];
}

I wrote a plugin that specifically needs access to the import names to dedupe imports by forcing them to come from a single source. The plugin sits in between multi-entry and node-resolve. There is more info in the README of the plugin I linked.