For me, a version of the shoulder charge has to be allowed to prevent defensive concussions.
The safest way to stop momentum of a typical kick off run is to turn side on, tuck your arm in tight and brace for the impact. Having to complete a ‘wrap tackle’ puts your head and face directly in the contact zone - whether you go high or low. Go high, you’ll cop an elbow/forearm or a head clash (from the attacker or another defender), go low and you risk late footwork and having your head on the wrong side, or cop a hip or knee.
Similarly, look at when Tedesco got cleaned out by Kikau when Teddy was rushing across to try get Kikau in tough - simple physics suggests the only way he could ever have enough momentum/power to put Kikau in touch and not get knocked out himself would have been to lead with the shoulder.
But to re-introduce leading with the shoulder/bracing for contact with the shoulder, the rules would have to be made in a way that any risk of high contact is minimised, and anyone going high is hung, drawn and quartered at disciplinary. They’d probably also need to find a way of stopping the forecful/blindside shoulder charges that cause whiplash and can go very wrong if contact is also high.