Good night, dear friends & pet battles lovers.
Here is something I was thinking about recently. I've decided to write it down and send to @WarcraftDevs via Twitter as well.
Next expansion update: Pet Battles
Leveling: you can now level all your active battle pets to the maximum level of 30, up from 25.
NEW: Battle Pet socketing
Upon reaching pet level 30, you can use one of six types of sockets on battle pets. Effect is permanent, however you can change your socket any time, destroying the previous one. Only one socket works on any battle pet at a time.
Socket types and colors:
Red = +40 power
Blue = +160 health
Yellow = +40 speed
Green = +20 speed, +80 health
Orange = +20 power, + 20 speed
Purple = +20 power, +80 health
Adding socket to battle pet changes its quality to Epic.
Sockets can be sold for Polished Pet Charms, given for completing pet battle dungeons, etc.
Of course, socket values can be negotiated and properly adjusted for the sake of balance.
Also, logic wise, they can be named "power leashes" or "pet medallions".