Would it be possible for a person to join the Army SF then join the USAF PJ's?

The problem is the airforce rarely accepts prior service, even less uncommon Is for prior service to book a pj contract initially. If that person got in to the USAF they will most likely have to crosstrain. I have no idea why an sf operator would want to become a pj since sf does have medical sf sergeants but whatever I guess that's his decision, a weird one.