I think this is a great idea. The casual reader will type in the short url (giving the publisher tracking and control), but the expansion will be available long as the print issue survives. This still fails if only an article survives (by clipping, photocopy, etc), but that seems like an acceptable tradeoff.

And until it's a common idea it would be helpful to annotate such shortened links so that someone unfamiliar with the publisher will recognize them as having a printed expansion included. Superscript "*" usually refers to a note on that page, so perhaps a superscript ">>"?

Exactly, or even just issue a yearly book containing the entire mapping. That would save printing since most people probably don't currently care about the expanded form, though in the future they would still be able to look it up in the library system. (They could also start doing this now, while they can't just retroactively add the expanded forms to editions they have already printed.)

Does any existing publication do this? Because providing both shortened and full URLs like this sounds like a great (i.e., retrospectively obvious) way to achieve a balance between "UX" of the magazine and longevity.