I believe with 0.9.5 as it stands it is possible to do either, but not both.
I can see the logic behind your preferred permalink, but I really really really don’t understand why you’d want to refer to a page by a second URL. (I can see why you’d want to reference featured content by a permalink, like in webcomics - latest one is on home page, but there’s a permalink for when the cartoon moves to the archive.. ideally in that case 123.html already exists, all that is happening is that the home page is repeating the content).
I just don’t get why you would want to have
http://tiltedsymmetry.com/Articles/Blogging/What-are-PermaLinks.html
AND
http://tiltedsymmetry.com/103.html
as the PageRank implications are bad.
I know that some changes were made [edit: as OpenGeek says] to stop multiple pages being available; I don’t know whether that’s toggle-able, but in principle it should be hackable out or (as I’ll come to in a minute) coded around in a flexible way.
Personally, I just treat aliases as set in stone; I don’t include category level stuff in the alias because that’s all highly likely to change as you say.
At some point I’m going to look at some smarts for the 404, so that page names that are not recognised by MODx could run through a custom routine to find the most likely page that is meant and redirect accordingly (eg "Articles/Blogging/What-are-PermaLinks.html" might find "BestPracticeBlogging/What-are-PermaLinks.html"). Such a routine could also twig that a numeric page name probably refers to a document ID and redirect to the right page.