In our project, SPIP (www.uzine.net/spip), we're using a similar list, Interesting, you'll have to let us know how it works. :)
Currently we have 11 languages and 2 more are almost ready. What's interesting is that the web interface includes arabic translation, with some bidi trouble ;)
The first split to occur will probably be between two languages of the cpf family (French Creols and Pidgins) - the Reunion (which is complete) and the Caribbean types (which is starting).
and a web interface to edit them. It works really well. We have plans to do something similar, initially for Zope, but ideally (at least in my mind) open source projects in general: http://dev.zope.org/Wikis/DevSite/Projects/ComponentArchitecture/Translation... Now we'll see if we get some free time to actually work on this. ;)
I remember we had discussed this idea a while ago on the Mailman list. I'm glad to see that it became a wiki think. If you want our code, you can have it (but eeeek it's php).
-- Fil