Accents, languages and literature usage would make this a bad idea. Not everyone can speak fluent English, and you couldn’t translate it on live because iPads are not quantum computers and quantum computers don’t even exist yet. (Quantum computers transmit data faster than the speed of light). Someone who speaks HRP (Queen’s English) will not understand a word of someone who speaks Jordie (Newcastle).
However, probably the biggest threat to this idea is that people will just chat on it and use offensive language at will. Not everyone will remember every single phonetic letter for their callsign. And to pronounce nine as ‘niner’ so the Germans don’t get confused.
In principal, this idea is excellent and should work brilliantly. I highly suspect the Devs have thought about this but have taken the wiser option, with probable similar thoughts to me with this issue. It won’t work.