Replacing face of a rigged model with a prettier face

I have a couple of well rigged models (including face) acquired from an animation course but the faces look quite unattractive (to me)). But the rig itself is well done and complex.
Is it possible to re-do the face mesh to look more attractive (perhaps to resemble some celebrity)?
How difficult would that be?
I’d really appreciate some answer.

Do you have any image reference?

You can remodel to your heart’s content, but you’ll most likely have to redo the weight painting.

I am posting an image. I wanted to send the .blend file but am not sure how.

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