add the ability to animate the mouth (see image bellow)

(also i used assorted allays resourcepack)

I use the custom player model voice chat addon. it lets the mod simple voice chat change the models in custom player model when speaking. It is a bit complex to implement though as you have to know how to use custom player model's editor and basically add a mouth model. works well once done though

That sounds like a solution @Spac3B3nd3r. Is the code available somewhere to adopt it?