[snip]

I doubt Conan Doyle's or Verne's works in Latin will ever appear.

You of little faith, a 15 seconds search gave me : http://ephemeris.alcuinus.net/holmesiaca.php (via https://la.wikipedia.org/wiki/Arthurus_Conan_Doyle)
You often just have to search, as I said earlier, latin is still a vivace language (and I've got 'Harrius Potter et Philosophi Lapis' on my library)
We shouldn't before we even began (and that's why this list sound like a good idea to me).

[snip and separate private mail about UN copyright]

Maybe somewhere in http://wikisource.org (sourceswiki)?

IMO, it is the best place for something applicable to multiple wikisource sites.

Ok, I'll start there.
Beginning on the Scriptorium : https://wikisource.org/wiki/Wikisource:Scriptorium#List_of_most_translated_works feel free to join.

Cdlt, ~nicolas