My SO loves standard poodles and the picture of the two poodles in the front seats gave her a grin on a very rough work day (12 hours of hair pulling frustration). Her poodle insisted on sitting in the passenger seat, so she got a seatbelt harness for the dog.
I agree with what others have said about the dog box. Dogs are pack animals and want to hang out with their pack. Isolating them in a box on the bumper would be emotionally stressful for the dog, and you often have little control with someone rear ending you. I've been rear ended twice and there was nothing I could have done. Some clown plows into the back of your car and the dog is toast. Inside the car they have the benefit of the crash cage and other safety devices humans have.
Additionally I would think riding on the bumper would be pretty bumpy. In front of and behind the wheels gets more up and down motion than between the wheels. Something most kids who have ever ridden a school bus know and the "cool " stake out the seats at the far back where the ride is more entertaining (for a kid). This is true for anything moving around, the further you get from the center and pivot points, the rougher the ride.