Based on the idea from Spratster_ on the forums.
http://www.minecraftforum.net/topic/1900477-villager-tweaks/

A cured villager zombie have a chance to spawn with 1 extra reward trade. That trade would be something nice, better than regular offers or maybe even unique that can't happen in normal trades, like diamonds.

A reward trade could only be used once, after that the trade doesn't get locked, it disappears. If possible, that trade will only be offered to the player that cured the villager.

If also possible, that trade would have a star on the GUI, or some other icon.

The reward item should be balanced around the cost to cure a villager:

• 1 Golden Apple (8 Gold ingots + 1 Apple);
• 1 Weakness splash potion (Mid game, requires access to the Nether);

Rewards could be (not final ideas):

• Diamonds for emeralds;
• Emeralds for rotten flesh (easter egg);
• Cheap silk touch book (rare);
• Cheap XP bottles;