I think both nix-env and flakes are designed with making package management easier. Nix-env tries to make it intuitive and familiar for new users. Flakes improve package management by simplifying the configuration.
Personally I would love to see syntax highlighting, language server, code completion. Maybe all in a dedicated application which is configured to give the easiest experience for new users. If nix is intended to be managed through config files, then the experience of writing a config should be as easy as possible.