The first experience for new users to the English Wikipedia
This sounds like an excellent collection of ideas, especially moving into userspace new low-quality articles that would normally be deleted, which currently has to be specifically requested by the author after the article has already been deleted.
However, I would dispute the notion that all self-promotion articles are created in bad faith. If it's someone's first contribution, they may not understand that Wikipedia should not include pure advertising material. So it should still be deleted, but with a good explanation to the user why such content is not accepted.
Also, I think we need to cut down, not increase, the use of canned template messages. They feel very impersonal, and it's obvious when you get one that it wasn't written specifically for you. I will admit that it's better than nothing, though, which (going by anecdote) is the most common response at the moment.
Anyway, between automatic storing of unfinished articles in userspace and moving such articles out of mainspace rather than deleting them, I think we're rapidly approaching a potential solution to the don't demolish the house while it's still being built problem, which is one of the most frequent complaints on this page and elsewhere.
I really like the idea of moving an article into the author's userspace rather than deleting it. :-) imo that would solve a lot of frustration and anger problems, and not just with newbies. Even if the article isn't suitable at all for Wikipedia, the author might want to put it in a blog or an email or something. Who knows? Deleting it totally is adding insult to injury, and really is unnecessary. (I feel the same way about so-called 'merges' which actually consist of deleting one article while leaving the other as is. They're properly called 'deletes and redirects', but some Daleks realized they could get more buy-in if they suggested articles be 'merged' rather than 'exterminated'.) As for 'restoring' a deleted article, I did that once and only got the latest version. Which was not at all useful as the content had been edit-warred over for months. I was 'helpfully' told it was my own fault and I should keep copy of all my edits. As if. ;-)