How to define %category% for custom taxonomies?

Question

So when you put %category% in the permalink structure that tag will be replaced with the path from the root category to the furthest subcategory, where, when placed in multiple categories, it will take the category order in account.

So how is this possible for custom taxonomies?

I came up with the following code: http://pastebin.com/pVyKzryS

I was wondering if someone had a better way to accomplish the same?

Answer 1

This will probably be easier to do when the following filter lands:

http://core.trac.wordpress.org/ticket/18752

Update July 16. 2012: Fixed.