can I choose any voice? would love to read software engineering books in voice of Morgan Freeman, or maybe even better, Scarlett Johansson

no, but this will allow you to: https://github.com/cpttripzz/Chatterblez

The voice of Mickey Mouse would be nice.

Why not Stephen Hawking ?

Because the Stephen Hawking voice spends a quarter of its time joking/complaining how it never got a Nobel Prize.

Yeah, could be a buff like 500% brain supercharge.