As the Head of Training of a Commercial Flying school in my secondary duty we don't take in none FI(A) Instructors. We want them to have come through "the ranks" and have taught all the levels and be able to teach all the levels. I am a Captain on the Embraer jet for the day job and I can tell you being an airline pilot means jack all when it comes to teaching. Trying to jump into the food chain ahead of guys serving the time won't endear you to them. My advice is do the FI(A) get the teaching experience and un restrict it an the advance.