Not to put a damper on your topic, but it seems like Mike Austins swing is something you might be able to do on top of the "modern swing" as you put it. I can't really tell what's different except the "throwing the arm" bit. This seems like something you should NOT attempt to do unless your other swing mechanics are nearly perfect.
You can find out more about his swing here: http://perfectgolfswingreview.net/austin.htm
Maybe someone more knowledgeable can shed some light on the differences.
A modern swing has its limits as well as an Austin swing.
What many modern swing systems have done is to add excessive cordination with timing.
Injury happens due to the player wants to hit it longer but cant due to the system itself wont allow longer without going outside their limitations.
If the player reside inside the golf systems limitations then they be fine.
When someone would say that having athletic ability would be worse to have when swinging a golf club is pure lies spread in the golf community.
The more athletic a swing is that helps with timing and action as its easier to do than a position based swing which a modern swing would make you do.
While both can be mastered the modern swing will make you a short hitter and more inconsistent and will risk the chance for injury.
Anyone says otherwise they are lying or being ignorant.
An austin swing will make you hit longer and will lessen the risk for injury by having a more athletic approach.
It dosnt mean you cant be injuried or that there isnt positions to match but we are dealing with relevances of chance here.
People can be injuried in baseball if they dont warm up at age 50 decided to do a home run and then strain a muscle.
Cant blame baseball by being stupid at the same time.
If you dont have an austin trainer close by you either need to travel or spending a lot of time mapping what they want you to do online and its likely you are better off with a local teacher one you find suits you no matter the swing system they teach.
Finding one good can be a hassle though.
The difference with an Austin swing is distance but also increased accuracy with lessen dispersion patterns.
The guy I apply this for was a 300 yard hitter with the old modern swing but also caused back injury.
He wasnt that long when we started out but the distance gain I helped him achieve caused him stress and injury due to modern swing limitations
Currently I am assisting him to be a 350yard hitter within the realm of the austin mechanics while increasing accuracy for the game of golf.
No issue with his back or injury anymore though.
And before anyone asks, no I dont teach amateurs currently as I only interested in tour level performances.
if your a PGA or LPGA player then I am interested.
I have been using a swing that was learned by following the 5SK, and more than likely not an Austin swing.
Last night I was "going for it", because there was a girl next to me that hit 250 yards (with range balls) and I did not want to be out hit by her. I probably swung my driver 20% faster than normal, and did not injure myself at all. Just my ego from hitting many long fades, draws (unwanted ones) and hooks and having a horrible finish to boot.
Learned two things from this. One, don't try to outhit a highly nationally ranked high school girl. Second, stay within yourself to make sure you hit them straight.
No physical injury from doing it, and probably could have swung up to 30% to 40% faster without injuring my body. Equipment or Ego are another thing.