My opinion:
Shoulder Charge needs to have forward momentum, hence the "charge."
It also should be contact above the shoulder. If I have a 100kg+ bloke running full tilt at me while I'm a little off balance I'm bracing for contact and at best hoping to slow the bloke down and not get killed. That shouldn't be a suspension.
As for those that argue that it can result in injury etc etc, whilst I agree it is a contact sport and convention tackles go wrong too. What about the defenders welfare? Going low consistently has a risk of copping a knee to the head.
Whilst it could be argued that the NRL may be liable for injuries etc, why not classify a shoulder charge that does not have forward momentum or make contact with the head a grade 1 offence that carries a fine. Contact with the head with no momentum is grade 2 and would result in 1 week suspension and forward momentum with contact above the shoulders is a serious offence and would rub the player out for no less than 4-5 weeks.
Make the obvious offense big penalties while the smaller ones carry fines.