Why don't you have __() handle the strings as they are accessed? You did not discuss what happens inside __() so I do realize that my suggestion might not be easy or even possible. But i would think that the process would be:

1. call __()
2. look up the translation for given language for given string
3. return the translated version if found
4. if not there, add it to the database and flag it for the translators to add a translation
5. return the string as is if no translated version is available

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)