The XF is quick and maneuverable.
This may either get your son into or out of an accident.
If he does get into a wreck, these cars are quite safe; I had a friend go airborne into the side of a mountain - car totaled, driver chipped a tooth, passenger sprained an ankle.
Also, these cars have a yaw sensor, and will take measures to keep your son from loosing control by reducing rear wheel torque and selectively apply brakes as needed.

Bottom line, if your son wants a Crossfire, he is telling you that he wants to drive fast, and he will only be happy with a cool car that is fun to drive.
The important thing is that he does not get hurt or into trouble doing so.
If I were in your shoes, I'd get him something fun, and get him into AutoX so that he can find the limits of his ride hitting orange cones instead of trees and cars. Also, getting some of the "zoom zoom" out of his system should save him a ticket or two.

If he can become a good driver, and a 4.5 gpa shows that he can focus, a car like the XF is more likely to get him out of an accident than into it.

P.S. - If you buy him one, I will be retroactively quite jealous.