Then you can just use ESM straight in the browser... The payload will be bigger, but it's all JS turtles the way down. I think for me the only small down side

Then you can just use ESM straight in the browser... The payload will be bigger, but it's all JS turtles the way down. I think for me the only small down side (beyond request count/size) is you couldn't use JSX and a lighter interface (preact or similar). One option would be a service worker to transpile JSX on demand... which I guess wouldn't be too hard to do.