While I was creating translations within my app, I just thought it would be great if Gii had a tool to do it.
Gii could scan your whole project for the usages of the function t() and automatically create the language files for it. It could then update your existing translation file by removing the unused translations and adding the new ones, maybe even sorting it alphabetically and adding useful comments like where the translations are used.
After that you only have to fill in the missing translations and you’re done.