i think it'd probably be something in the feral tree, since balance tree's got the moonkin form and resto's got the tree of life form, so dire cat's a good thought, and since WoLK is in the frozen land, maybe it'll have a snow leopard look.  or combine cat form and travel form to run up to em fast and smack em around before they know what happened.

of course, if you gave the cat form a 400% armor increase, then they'd probably let rogues start wearing mail or something, since cat form emulates rogues, just as bear form emulates warriors and dire bear emulates warriors with plate