At the moment the voices in waze are standard. I think this can be improved massively in 2 different ways.
Every profile, on the website, should be able to load different recorded voices for all the commands required by waze to operate. Once saved and with internet access on your phone, you should be able to get them loaded automatically and be ready to use them immediately. In case you make a mistake, you should get them back to factory settings with the click of a button.
On the other hand, Waze could team up with different people (BA Barracus for argument sake), charge the users and get personalised voices at the client's will