Darth I don't think that kind of protection could be right implemented.
Imagine this scenario.
A new player creates his brand new world.
An old player send him 5 death stars.
As he has not any building he can attack you but, Ups! He is 50% lower than you, so you can not attack him.
I can imagine abuses like multiacount with noob protection always 50% below the media and suddenly one of them Top 1 (remember you can give your ships to lower players).
Noob protection is interesting, but coders should be very carefull.