We've had this phased license system in portugal since forever, and while painfull, it does work.
Our original system was 125cc, 15hp from ages 16 up (A1 license),
then from 18 you could get an AL (A Limited) license of maximum of 25 KW (33hp), untill ONE of the following occured:
- You had 2 years with and "A" license (both the 125cc and the unlimited cc license apply for this).
- You were over 21, AND did a test on a bike with more than 35KW of power (46hp)
So you could get a BMW S1000RR on your 18th birthday, IF you had passed your A license on your 16th birthday.
It worked well - you could jumpstart to big bikes pretty easily. (remeber, over 21 = straight into bike bikes license).
I believe this new intermediate (A2; 48hp)license is a good idea. A good little detail is that you cannot restrict a bike to more than half its HP - no taking an R1 and then restricing it to 48hp. THis is because the people that drafted this know full well how restricting bike's power is: You restrict it, get it approved, and then when it leaves the shop it magically becomes unrestricted.
Opened up a huge new market for intermediate CC bikes - CB500s, NC700s, the 250s... And the other makers are bound to jump on the 48hp bandwagon. Even limited 600ccs; as long as they don't have originally more than 100hp. (Yamaha XJ6s Kawa XJ6, honda CB600s....).
And prevented 18 year olds from wrapping themselves around trees while riding 150hp monsters....