Would it be possible to write a bot which simply goes through all the pages, following all the interwiki links that currently exist and placing them where they don't exist? This seems like it would be very easy for someone to write, easy to implement, and very effective.

For example, if an article on EN links to an article on ES, but that one links to an article on DE, then the bot will go back through and add es/de to en, en/de to es, and es/en to de, etc.

This would eliminate a lot of the problems encountered by the Interwiki Link Checker, for example, which can't deal with comparing English and Chinese (provided that at least one page somewhere in the chain links to the Chinese version).

Of course, it isn't a complete solution, but it seems like it would be a very effective one. For any chains where there are discrepancies (en -> de -> a different en), it can just not bother with that chain.

brian0918