It's a pretty hard thing to rort if you need to have three ruled out with concussion. I doubt everyone's going to fake ten concussions in the last twenty minutes. It would be pretty obvious.
HIA currently doesn’t count as an interchange does it? Because the system is rorted every game if they are not counted. Around the 20-30 minute mark of matches there seem a lot of HIA replacements.
They need to go further with this 18th man decision.
I think they should add 3 development players to the bench to be used for HIA. One Forward, one back and one utility. Development meaning outside the top 30.
They can only (and must) be used for HIA. They can be used as a normal replacement after 60 minutes.
This would solve the problem of HIA but also slowly introduce young players to First Grade.