Esbuild does have a JS transform API, so you could write a command line tool that walks the file system (Babel, ESLint, Prettier, etc. all do this so you have e

Esbuild does have a JS transform API, so you could write a command line tool that walks the file system (Babel, ESLint, Prettier, etc. all do this so you have examples), transforms each file, and writes the code back out. Snowpack's build command also does this.