If what he wants is to become a nurse anesthetist, then he will have to do some ICU nursing first. That’s who they take for nurse anesthesia programs, because they have a lot of familiarity with managing ventilated patients, some of whom are also on cardiac meds, and have other very complex issues. They’re the ones who have a lot of experience with nursing critical care patients. They like to take these nurses because they already understand a lot of what is done to manage a patient during surgery. So if that is what he wants, the path would be probably a year of floor nursing while he applies for the RN to BSN program, then after he gets his BSN, back to floor nursing while trying to get into the ICU. Then as many ICU type positions as he can get (cardiac, neuro, pulmonary, etc) while he investigates nurse anesthesia programs and applies.
You’re right, in that if he decides he doesn’t want nursing, but wants something else, he would have to take a lot of other classes. But frankly, if he were to go for the AS and decide he wants to take something else, probably only a year of his coursework would transfer (the gen eds) and he’d still need to do at least 3 yrs more towards any other major.
To me, it seems that this is an excellent pathway. Absolute WORST case scenario: he finishes the ADN/RN at 18, and then goes to a 4 yr college to study anything else he wants. He’s finished high school with an employable qualification, better than if he’d just gotten a high school diploma.