1. Taiwan is officially known as the Republic of China (ROC). Its official language is Standard Chinese. Therefore, "Chinese" seems like a pretty adequate choice on WTM. Chinese should also be chosen for Mandarin, Wu, Cantonese, ... Those are considered as Chinese languages. Kazakh could be added. Only kinoute can make such additons, though.
2. Tagalog could be added (with the Philippines flag).
3. Our problem for Arabic is: Which flag should this language be associated with? As for Hindi, as an official language of India, "Indian" seems to be a good choice for WTM.
Keep in mind we're not trying to be perfectly accurate, the system's design being flawed: Flags (therefore countries) associated with languages... It's intuitive, though. Let's work with it.