These are interesting to me as a notebook user, because a lot of these I see as advantages of the notebook design.
(1) This is better to me, because it makes notebooks more consistent and easier to jump into. I read english prose sequentially, why not code?
(2) You can do this in all environments I've used with <a> tags.
(3) this would be nice, but I'm not sure it's worth the tradeoff because the editing environment wouldn't correspond as well to the exported document.
(4) true, but I have a vim plugin that make it better
(5) also true, but this is a good thing for simplicity. I don't want to have to keep track of the lexical scope of multiple language environments
(6) There are tools for this, but yeah it's not great. The main issue is saving outputs
It sounds like the goals of notebooks vs org mode are slightly different, at least the way I use notebooks.
For me, notebooks are a tool for sacrificing control and programming flexibility in exchange for easier collaboration and visualization. It's harder to write structured code, but it's much easier to share with a large number of semi-technical people.