In my experience, if a car comes with satnav, Avis doesn't try to deactivate it - although they won't tell you the car is satnav equipped in advance, so if you've dropped money on WhereTo?, you're going to have to go back to the counter.
Re: satellite radio activation - when I got my Fiesta last summer, the satellite radio was activated as part of the delivery process, so it's possible that if Avis (rather than a dealer) does the delivery, they might bypass the satellite radio activation step.