There is no answer to question:
realistic; power restriction dont work, if u really want the power. Ok All powerfull cars are ban (skyline,s13,180sx,s14,s15,ceffy,hsv,ex6,rx8,rx7 etc etc) wat is stopping any P plater from going out buying a ae86 and dropping a sr20 into, he add some boost and he can run 200+rwhp in a car which weight less than 1000kg.
I guess i am agaisnt restriction in away as i learnt to drive (yes on my L's) in my turbo skyline, i am now on my P's and have not had a crash or anything yet (thou i have spun out 2times and have learnt from those events) i do have 2 speeding fines one i wwas just like 6km over the other was 20km over (which yes was very stuipd, but i learnt from it and now find it hard to speed 10km over the speed limit). But i can see that if restrictions where made law, i wouldnt have a problem with it my sister is having a baby and my gf is just starting to drive, i dont want some dickhead p plater to kill them just cuz he couldnt controll his turbo car.
maturity, i think is really the KEY, if someone isnt mature enough to see that there actiong are just plain stuipd then there is nothing any laws can do to stop them.