To me the proposal there is arguably even scarier than what AMP is doing now.

It requires changing browsers, to let people distribute Google Hosted Apps on their own domains (as long as Google approves). Sites distributed in this way will get preferential treatment by Google.

This is essentially an App store model, similar to Google Play, and the really big danger is that we end up in a place where you either distribute (and host) your website through Google's AMP registry, or you're not actually on the web (in the same way that distributing your Android app as an APK outside of the Play store is not a realistic distribution channel).

I hope Firefox, Safari and Edge will resist this.

No. In fact, the solution detailed in that article accomplishes the exact inverse of one of the letter's demands.

While the letter wants third-party content not to be surfaced in a wrapping viewport that downplays the fact that it's actually Google's AMP Newsreader, the recent AMP announcement details a planned change where emerging tech [1] will be used to make the URL appear as if the content was directly loaded from the distant origin, because the content being served has been digitally signed by that origin and its serving has been delegated to Google akin to how a run-of-the-mill CDN is delegated the authority to serve content for a domain that's 'spiritually' owned by someone else.

However, the recent AMP announcement does address a very frequent complaint about AMP. Just one that's at odds with the one the letter is requesting.

[1] https://github.com/WICG/webpackage

That is a great article because it sheds light on actual technical reasons for the current behavior. The original article is pretty light on technical details of how to achieve their suggested goals, which is weird because it assumes the user knows/cares about URLs, and that is probably only true of those with more tech savvy.

In theory it does, but there are a lot of open questions there (including whether Apple will implement it). I'd say the search engine placement is the bigger of the two issues anyway, as it clearly shows Google putting their thumb on the scale.

1. H2 2018

2. Relies on a "web standard" that Google is pushing and is implementing in Chrome (and so far, I think, only confirmed to be in Chrome)

The letter is undated so it could be old and I'm sure they'd prefer if URLs get fixed immediately rather than in a few years.

Update: So after Google announces that they're fixing AMP, some people decided to write a letter demanding that Google fix AMP? I guess the next step will be to retroactively take credit for Google's changes.