[r_hoods_ghost]

This is basically what you do currently for a TTS engine if you have ALS or similar. The search term you want is "voice banking". You are given a long list of words and sentences, often complex, to read out that have all the different sounds and then these are re combined by the software. The problem is that by the time you know you need this, you often already have speech problems and so making clear sounds is difficult. Also if you're like my relative who was trilingual you would need to do it in all three languages using the current system. She got a half way decent voice bank in her native tongue, but it was still noticeably slurred. She didn't even attempt it in her second and third tongues.