> These are all solvable issues with fairly obvious solutions.

No, they are a can of worms and decades of arguments and incompatibilities and versioning

> But the latter is already handled by iframes

iframes don't handle this case because the page can not adjust to the iframe's content. There have been proposals to fix this but they always run into issues.

https://github.com/domenic/cooperatively-sized-iframes/issue...