With the addition of English voices to the game we now have 3 different voice language. Sadly, you can not switch character language without switching the entire game to that language.
I personally would love to play with English Lee since he sounds cool, but I also really like Japanese Selena.
An example of how this would work in practice can be seen in games like XCOM and Arknights. Both games allow you to pick the language, for XCOM it's the language of your soldiers separately per soldier, for Arknights it's a language per operator.
I don't know how easy it is to program something like this in when the language system is already in place so I recognize that in may not be possible but I do hope it would be considered.
English Dub Feedback:
The dub so far sounds amazing but some characters feel like they are missing the liveliness that the japanese version has or straight up try way to hard to sound like anime. A comparison I would like to draw is between Lee and Pualo.
Lee is perfect, soft spoken out of battle yet fierce in battle. His combat limes are short and gritty and fit the theme of battle.
Pualo sounds like she is shouting the names of pokemon moves from the early pokemon dub. And I mean this with all respect, I think the voice is amazing but it lacks some of that combat flair. (maybe that's just me tho, others might have a different opinion)
Lastly, I hope to see some more variety in the accents in the future. Selena for instance has a whole German theme around her with even her theme song being an old German poem yet there is nothing left of that in the english voice sadly. Arknights again does a phenomenal job with this, 2 characters (Ebenholz and Czerny) are both from a region based on germany and this reflects heavily in their English dub. Maybe asking for a retroactive change is a bit too much to ask but I hope you will consider this for future characters.
This was my TED talk, I will now be taking questions.