Really like the idea I think it would have to be "summoned" or something from an item, like ppl said earlier.. Like a trinket or something, summoning a cool drake that wont have an xp-bar. And I demand that the hunter can use it as a mount when out of combat.
A cool ability would be if the pet had ALL the buffs available to pets in his spellbook, but you can only use one of them at a time.. BM hunters could choose to use BL/heroism & kings & priestbuff aswell tho. This would of course make all other pets obsolete for that tier, but the ones QQ'ing because they HAVE to use a legendary pet should just stfu.