Blue card rule seems silly to me. They have independent doctors, and the ref is not going to be medically quialified, at least not in most cases.
Not sure how I feel about the interchanges really. Might stop abuse of the current rules but then likely to lead to more players who can't last 80 or even 60 but can do 50 over two 25 min stints and so can smash people, go off for a rest and then come back and smash someone else who's played 65 mins already. I think they'd have been better off just closing the loopholes which allowed the previous abuse