How to get player's face onto character mesh

Not asking for a complete solution here (though if someone can point me to an asset store asset, etc, I'm game).

I want to be able to let players put faces onto characters in my game.

I'm wondering what's the approach for this? I have a generic mesh, for the characters, which I'll use in all cases - I can ask the players to identify the mouth/eye/chin areas if needs be, and or ears...

I then want to take their photo, and some how use it as the mesh for the characters face...

I guess I need a means to edit the texture at runtime, and also flatten the photo, to match the flattened texture...

I also thought about projects (i.e. projec the face direct onto the mesh ) but I reckon it'd look bad and have bad performance.

Any ideas?

Pseudo-code, code, unity docuentation links, or just random thoughts are welcome.

Thanks