If you're fatigued - then you don't have the high intense energy to complete in a wrestle. Therefore, I suspect wrestling will decrease.

Either because a) they're too knackered after wrestling for the first part of the game
or
b) wrestling will decrease as a measure for players to conserve energy throughout the whole 80 minutes.

Like which other gimmicks?

There are also a few other measures including a time clock for breaks in play, which add to rule changes last year designed to make the game faster and the players smaller and fitter.
The play the balls should be quicker because there will be less wrestle and less numbers in tackles, so the game will speed up.

It shouldn't make the game look much different from the stands, but smaller and fitter guys will thrive more, and that will lead to teams that win with small guys running big teams off their feet.

Even this year, with the changes made last year, the game is a bit faster and the players need to be a bit fitter.

I think it is working well, and look forward to see how it works next year.

They still have that in the NRL since Perenara is still employed there....

Great idea, better use of subs and tacktical changes on the return, better than just swapping all the time, coaches will have to look at using 5-6 changes up to 60-65 mins keeping the other changes in reserve for injuries in last ten mins.

I'd cautiously back these changes (the 8 interchanges from 5 subs). It hopefully might go someway to mitigating the effects of huge increases in power and strength of the players in recent years.

Though I think if the aim is to clear up the ruck then that can be done by the referees penalising holding down, interference etc.

If we think the play the ball is too quick and we want to avoid the cannonball tackles and twisting techniques then firstly we can harshly penalise those who commit them but we can slow the play the ball if we wish, again through the referees. They can penalise poor play the balls.

If we think there isn't enough space for half backs (which id agree with) then in addition to these new interchange rules we can tweak the playing rules. A simple rule change as to when the ball is in play and so when the defence can move up at the play the ball would help. Change it from the point the player touches the ball with his foot to the point at which the acting half either passes or runs with the ball. That'd give the attack an extra second or so to get the ball away from the play the ball and so give the first receiver a little extra time on the ball. Combine that with penalising offsides and not square and also harshly penalise "late" hits on the halves. I say they're late they're generally not, they're often timed just right.
If you want to give halves more room in which to work I'd also suggest looking at re-introducing competitive scrums.