The breadcrumbs are actually built in to Mediawiki, and automatically generated. I will mention it to the Translate developers, to see whether they have any ideas, but there's nothing we can do in terms of mediawiki syntax.
I'm told that changes need to be made at code level. We have a "volunteer" that says he will try for it when he gets home in a few days. (For "volunteer" read "press-ganged volunteer" :-D )