I'm all for tiered licences. In Belgium already learner drivers are not allowed to drive during the night and weekends. I certainly wouldn't mind that be continued for some time even after they get their license.
Same for more powerful cars. At the moment there's only a rule that under 21 can't ride a +25kW motorcycle. I would applaud if that rule be expanded to anyone's first year(s) of riding after getting their license. And expand it to cars as well. It is utterly silly that an 20-year old cannot ride a +25kW motorcycle but can without any problems get into a Ferrari and go street racing.

I don't really agree with you about the motorways. It is perfectly legal for learner drivers to ride motorways in Belgium and it does not cause any problems. In my experience, having taught 2 people to drive motorways are probably one of the easier roads to drive on. The speed may be higher, but there's a lot less things to keep rack of. No oncoming traffic, no traffic lights, no intersections, no cyclists or pedestrians, ... My experience is that learner drivers find driving in the city a lot more stressful and difficult.