Hello,
GerardM and I had a long phone conference about localization requirements, and we've reached a consensus.
Cormac raises a valid concern about the difficulty of localization alongside all the other tasks of opening a new wiki, but the new requirements actually mean less work is needed for the first project. The previous requirements called for the translation of around 1400 messages for the first wiki, and around 200 messages for the second wiki. The new requirements only call for the translation of 500 messages for the first wiki, and 1700 before the second wiki is approved (by which time many messages have usually been translated over time by the first wiki's community).
Even though the new requirements include all extension used by Wikimedia wikis, this is redistributed so that the difficulty of opening the first wiki is reduced, and localization can be done slowly over time until the second project instead of in a huge one-time batch.