Hey Link, here is a hetero female replying... Just my view...

What's so wrong with changing the definition of marraige? That's what amendments are for right? Sure people could call gay marraige differently, but I feel that because there has been such struggle and turmoil to even be recognized by the state that if I were in that position, I would want "marraige" to apply to me too.
On the other hand, if I had to call "marraige" something differently, I would also call it Union of Souls. Sounds more ethereal and romantic.