The Rollup tool supports that in conjunction with the `preserveModules` option. I've never used it outside of playing around, so can't vouch for it from experience, but yeah it exists. It can also do more of course, like convert to older module formats or the like, but obviously you don't need to use that.

The biggest downside is that even in http2 or http3, bundles can still perform better in terms of lower overall loading times, since individual modules you need to download the first one, and perform at least a bit of parsing to find the other modules statically imported before you can start downloading those, repeat.