I've been working on this full-time since late 2025. Happy to share what I've learned - feel free to email me as well if you wish to.

> so it doesn't support classes, asynchronous, destructuring

For users, this general category of problems (not knowing these edges) is the hardest. It's amplified if you pull libs from npm. One of the best ways to test compatibility is to test with non-trivial projects, or existing codebases. For example, one which has helped me a lot is trying to compile Microsoft's typescript-go compiler, after translating it from golang to TypeScript via a separately written tool. Large projects surface a ton of issues.