Smarter default for back-end

Provide a mechanism that uses some guide to determine the "best choice" for backend on translation. e.g

B1 is best at Spanish and Japanese but poor at everything else, B2 provides only EMEA locales but is pretty good at them, B3 does everything 'ok'

• requests a Deutsche translation: B2 is used

• requests a Spanish translation: B1 is used

• requests a Japanese translation: B1 is used

• requests a Chinese translation: B3 is used

The system administrator can set these rules somehow.