Marriage Equality

The topic of marriage laws came up in a Facebook discussion today, and I broke a months-long self-imposed abstinence from political discussions on Facebook to reply to it. I guess that means it is somehow relevant to me, so I figure it would be a good topic for my measly little blog here.
I take a pragmatic approach to marriage and how the government defines it. I see the legal recognition of marriage mainly as a financial concept. A state-recognized marriage allows the participants to:

• claim the other as a dependent on tax forms if only one works
• enjoy automatic transfer of possessions in case of death (depending on the state)
• cover the other with employer-provided health plan
• act on the other's behalf with automatic "power of attorney" in many situations
  etc, etc.

Which of these items is closely associated with religion? As far as I can tell, none. But marriage is a religious concept, and different religions define it differently. Some allow one husband to have several wives. Some might allow two husbands. Some might even allow for multiple wives and multiple husbands to be joined in a single union.
As is the case with most religious arguments, each religion thinks it owns the "correct" definition. The problem is that in the United States, we are supposed to have religious freedom, but this particular aspect of religion has been commandeered by the government in a way that only supports one definition.
This argument comes to the forefront now because of the gay community's fight for equal rights, but I think it goes beyond that.
Let us look at the idea of a household, outside of the context of any particular religion. Let's say that two families, each consisting of a husband, a wife, and two children, decide that they could operate more efficiently by sharing a single building (which we will call a "house") and sharing responsibilities. One person will be a wage earner, because they will need cash to survive in this society. Everyone else will help out. They will save money on power, on appliances, home maintenance, meals - pretty much everything. Now, it comes time to do the tax returns for the one wage earner. Under current laws and tax codes, the earner is penalized with respect to other "families" because he/she can only declare the people in the household who are related through the concept of marriage as dependents. So he/she gets 3 dependent deductions, instead of 7, while he/she is actually supporting 8 individuals with the one paycheck.
Is there something evil about this arrangement? Is there something unnatural about it? I think one could argue that in the US, it would be "abnormal," but I don't think it would be inherently harmful to its participants or the society at large. In fact, with all of the energy and resource savings, one could argue that it would be better than if the two families resided separately.
I suggest that this type of arrangement should be just as acceptable in the eyes of our government as any other family, and it should receive the same benefits. I do not care if it is called a marriage or anything else. The point is that the government should not be in the business of defining how people define their basic living groups.
If two people who are unrelated decide to create a household together, the government should be capable of recognizing that without offending anyone. The way to do that is simply to avoid the use of the term marriage, which has certain religious connotations for many people. Leave marriage up to the religions, and be concerned instead with the concept of a household, or living unit.
The government already has mechanisms for creating entities that consist of groups of people. They are called corporations, or partnerships, or businesses. The is no reason why we could not have a "household partnership" that could be defined for any group of individuals who want to create one. You would expect that in the US, most of such partnerships would consist of married couples, but other groups would not be excluded. We achieve freedom of religion and equality all at once, and there is no real or perceived devaluation of the term marriage for anyone.