Cost Of Blend Shapes With Lip Sync On Mobile

I am doing lipsync.

Most posts that I have seen and the Unity documentation suggest having just one skinned mesh for character creation.

I have a character with medium polygon count, say 4500 tris and want to do 3D shape phonemes, and have 5 Blend Shapes and am aiming at more powerful mobile devices. I could try and do lipsync with bones, but it seems like morphs will deliver better results.

Any thoughts on how to balance speed and memory consumption?

It seems like a waste of data to include the entire body in the blend shape when you are only animating the face...