As far as I know, according to the official definition of the United Nations, there are currently six languages officially recognized as the world's common languages (i.e. the working languages of the United Nations), namely: English, Chinese, French, Russian, Spanish, and Arabic. There are four other important languages, namely Hindi, German, Portuguese, and Japanese. I believe that at least the above 10 languages should serve as the foundational languages for TMP.
I know it will be difficult to achieve this goal, but TMP officials should take it seriously and gradually improve the language system.