I think it would be nice if in the text-to-speech settings you could specify a cascading set of languages, with dictionaries, associated with each language, intrinsic in the language selection.
When, a word is encountered, TTS would look up the word in the dictionary for the selected language, if it is not found, it looks it up in the dictionary for the second language, and so on. When a word is found in a dictionary, it is played, using the language intonation for the language associated with that dictionary. If the word is not found in any dictionary, the first language specified is used to pronounce the word, by default.
This multi-language algorithm could be a bit more processor expensive, but several multilingual users who write their notes and text in their apps in more than one language at a time (even using the Feynman method, ie., write as text comes natural to you, rather than abiding by the rules of a specific language), for instance in their Google keep notes, might like this feature (and use it).
Can this be implemented in Android?
When will this be implemented?
How can I enable it?