I loved it to. I'd love to make a typed coffeescript variant, which transpiles to TypeScript rather than JavaScript. My pet name for this is `tycoscript`.
This already exists, see [1]. Development has a bit stalled, but afaik the author wants to keep pursuing it. There's even a Discord server for this kind of project, see also this GitHub thread [2] where CS+TS is being discussed in general. Alternatively, you can code in Coffee with JSDoc type annotations, yielding a near-TypeScript experience in both IDE and output, albeit the annotation syntax can be a bit annoying, ironically.