Of course, French is not officially supported, but I tried synthesizing French few times, taking advantage of cross-lingual synthesis. And I concluded that Feng Yi is currently the only voice who can sing in French.
The idea is simple: Just use her Opera parameter for simulating nasal vowels. Mandarin
A for French “an”/“en”, Cantonese
E for French “in”, Mandarin
o for French “on”, and Mandarin
a for French “un”; and set the Opera parameter to 150% on these vowels. This alone may render the nasal vowels too aurally distinctive, so tweak some other parameters as well; preferably Power to 50%.
Though the question is… Can any other voices do this? Personally, I pity over Ryo for his Nasal parameter doing nothing significantly noticeable. Nor there seems to be a global parameter that can simulate nasal vowels. What should we hope?