Apple is known to make irrational cases when it comes to their products, never heard of Sony lol.
I doubt they can make a case for something like this, otherwise the warranty would not mention anything about 3rd party repair services voiding it lol. They are acknowledging services by stating they void the warranty, thus legally the do not have much room for a case.
Anyways, if its something that enough people are interested in I'll pry open my Walkman Z. Otherwise I'd like to keep my Z boxed or at least looking new, the first guy to open his device is usually the one left with the most marks.
Think like this; You'd be doing a great job for the whole of humanity :P
Just GO GO GO!!! (Y)