Has anybody come up with a way to use Thunderbird to access Google
Groups, like a regular newsgroup reader?

I understand that the reason that this cannot happen by default is
that Google Groups does not offer NNTP access. However, Google Groups
does store plain text copies of messages, which can be downloaded from
suitable URLs. I can imagine an extension which would work like this:

- To access Google Groups, the extension navigates to the appropriate
HTTP:// URL on Google Groups, reads the various headers, and populates
the relevant newsgroup in Thunderbird accordingly.
- To download a particular message, the extension navigates to the
appropriate URL for the raw message and downloads it. Simple!
- The extension stores the users' Google Groups username and password
and logs into Google Groups using it for access to private groups and
to post messages.
- To post messages, the extension simply takes the message the user
has written, accesses the Google Groups submission form, copy-pastes
the relevant fields in the sent message to the relevant fields in the
form, and submits the form.

All in the background, so that from a user's-eye-view there's no
difference from using a regular NNTP service!

Is there any reason why this would not work?