If you'll permit me to expert two of your thoughts:

If we exposed a good set of APIs to JavaScript, then I don't think gluing will be much of an issue.

And if we did provide a good set of APIs such that web developers themselves can implement their own editing commands, then there's no reason we can't implement our editing commands in terms of those public APIs, putting aside, whether we should do it or not.

Notice that you take "a good set of APIs" to be a given, from which you start to reason about the value of a rewrite done in JavaScript. As Maciej and Darin have already mentioned, a good set of abstractions upon which to build editing is not a given. It is the critical part of the task. So far, I haven't seen a proposal for a good set of abstractions upon which to build editing. I'd like to see a proposal for that. I worry that talk of a rewrite and a new language is just a distraction from that real task. Geoff