Still a magically aged wyrmling dragon would be a neat villain to have in a game, they would have all the power of an old dragon with all of the maturity of what likely amounts to a human 6 year old. And if you defeat him by breaking the curses he is under after a long and arduous quest to figure out how, the PCs could just squash him, that would be very satisfying.
+1
Nice
Yeah it is really. The 12th~13th level PCs need receive a kill the evil dragon overlord quest. They learn in town that the evil 'Old' dragon came from the wizard's tower and the wizard had been experimenting with it. Contact Dead reveals the dragon used to be the wizard's familiar, which meant it was less than Young and in player who puts two and two together realizes those experiments meant to make it more powerful and ended up forcibly aging it. Little Divination later they learn they need...
Remove Curse: Removes Bestow Curse's +1 Age Category.
A picture of the dragon's true form: Removes Greater Bestow Curse's +2 Age Category, the effect is like Dorian Grey's thing, one look undoes it.
Greater Dispel Magic: Removes River's Ravages, which as the BBEG always has the opportunity to cast it before the fight.
Which puts two casters to use and a 3rd PC holding a picture screaming look at me to use in the first round massively debuffing the dragon down from Old (say red dragon for cr20) to a less than decent BBEG level. It leaves some room for them to skip some but not all of the debuffing.
Be sure to say the red dragon has Mantle Of The Icy Spirit(fb) to avoid Shivering Touch overkill.