Default category slugs

Alright, so I'm setting up a large amount of categories. Some of the categories will have duplicate names, but will have different parents.

For example:

Xbox (slug= xbox)
- Controllers (slug= controllers)
PS3 (slug= ps3)
- Controllers (slug= ps3-controllers)

What I'd like to happen is for the category slugs to always fill in the full hierarchy (like the ps3-controllers category did.) By default, as you know, the first category with that name will always have a slug of that name, and the second category with the same name will have the full hierarchy as the slug. Is this possible? and if so, is it just a plugin that I need, or where do I start editing?

Thanks for any help