You just can't win with the theocrats. You can water down civil union legislation as much as you like. You can bend over backwards to placate fundy sensibilities--despite this supposedly being a secular liberal democracy. The Federal Government will still knock it on its head, arguing that any legislation proposing the faintest trace of formal recognition of gay partnerships "undermines the institution of marriage." As if happily-married heterosexuals will abandon their marriages in droves and embrace buggery before the ink on the Bill is even dry.
Oh, well. The medievalists have to get kicked out eventually.
(For a decisive smackdown of the notion that allowing gays to be married "undermines marriage", see this post by The Language Guy)