Option to Defect from your Faction

(Posted here because I don’t have a sub)

I have a real simple problem. I want to play an Elf Druid, but all my friends are Horde.

So why shouldn’t I be able to choose the race I truly want, and then have that character convert to the opposite faction?

In the past I’ve heard the argument of “in PvP, it’s important to be able to identify a character’s faction by their silhouette,” but with all the “allied races”, I don’t think that argument holds much water anymore.

What other reasons are there? (I’d like to hear from you.)

If it’s a matter of verisimilitude, perhaps penalties could be imposed? (I’m already assuming there would be a quest line in order to defect and prove your loyalty to your new faction.)

Penalty ideas:
Your faction’s town guards don’t defend you.
Appropriate vendors charge you higher prices and/or don’t sell you certain products (like tabards?).
Opposing faction gets more honor for killing you.
…I’m open to others.