Second, would this impede the ability to remove
the "you've been logged in"
screen? Aryeh mentioned an idea that would allow MediaWiki to remove this
horrible workflow interrupter.
You may have noticed that I included a horrible page to log you in
instead of the content (the "lightweight page"). That can be replaced
Showing a login dialog and setting your cookies is easy. But what do you
do with the previous screen? You can return to it, but oh, you have
several more tabs, and it needs rollback links with tokens everywhere,
and there's now a need to highlight the links to pages smaller than 500
bytes, and replacing png equations with TeX. Plus you have a couple of
fired would have needed to do something different.
Using a separate page avoids skips that trouble. The LQTv2 you mention
will have that problem, too. Unless they join the you are logged in
action with the comment submit, or so.
Combining the login with the comment submission is probably the most
practical approach for LQT.
The AJAX login script I wrote for NetHackWiki usually just reloads
the page, but it's smart enough to click preview/diff instead on edit
pages and to follow the return link on Special:UserLogout instead. I
don't have it triggering on the "save" button like the LQT screenshot
showed, but if I did, it should be easy to just continue with the save
after logging in.