Thank you. The Dart team is very interested in feedback and requests for features. Some of the features you mention are already being worked on. Now that we are almost done switching over to a common front end for all the Dart compilers and tools, it will be much easier (and faster) to add new features.

We encourage people to submit issues and feature requests in github. For the Dart language, that would usually be in https://github.com/dart-lang/sdk/issues or for Flutter, in https://github.com/flutter/flutter/issues .