Problem with the "marriage has a history and emotion and yaddayadda*, let's not make it a business deal" is that right now (and forever into the past, more or less), it already is a business deal. It's never stopped being a business deal, especially since it was made a legal entity. It's only become even nominally not one since people stopped being married more by their parents than themselves (Note: This is really damn recent and still happens in many places, including the states.), but the business deal aspect has never changed, just been become likely to be ignored by people too enraptured by their partner's genitalia to actually know what they're getting into.
Incidentally, that's one of the reasons marriage screws many families and relationships straight to hell -- people thinking they're doing something full of love and commitment or whatnot when there is a whole hell of a lot more riding on the coattails of it. And then the divorce comes, of course, and *kaboom*.
In any case, the full realization of civil union rights wouldn't somehow entail current marriage candidates lose their status. There's no way in hell you'd be able to push through something that said marriage is only for white heterosexual couples.
*Not that the yaddayadda isn't important or anything, of course.
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Anyway, the ideal is to abolish marriage as a legal entity. That doesn't prevent marriage, it just makes it a strictly personal/religious thing (as it should be, really). It would actually makes marriage more of an important emotional/historical/religious step, because suddenly it wouldn't be a business deal -- you wouldn't be making the choice with that taint of legal coercion behind it. It'd be getting the courts out of your bedroom.
But. The trick is getting there. The easiest way to do that (and one of the reasons the bigot bastards are fighting equal-right civil unions, beyond the obvious) is get civil unions across the board entailing full-out the exact legal repercussions as marriage. After that, the argument becomes a lot easier (especially from a legal standpoint, from what I understand) for either naming it all marriage or abolishing marriage (again, strictly as the name for a legal entity) entirely.
It's also a lot more likely to happen if you can get it past the initial bigot bastard gauntlet, because most people don't know or care enough on the subject to actually realize what any of it entails. That's pretty obvious when you consider stuff like Florida's amendment two a few years back, coached as a 'marriage protection' (i.e. anti-gay marriage) law that's only real impact -- gay marriage already being banned by at least two other statutes -- was stripping some rights from unmarried heterosexual couples.