Virtually NO ONE as a kid aspires to be a punter in the NFL. Assuming your son (or even daughter) is a healthy kid, train them like Todd Maranovich's dad did with him.
Punting is NOT that hard. Take a decent gymnast and he could be kicking 50-yard punts in no time. NOW you start off your kid at 5 to be a gymnast and at 10 transition him to be a world class punter. 3 hours a day from 10 to 18 and he WILL be a very great punter. He can skip college and make WHAT? a million a year for 20 years? Game over.