But your examples are for available legal coverage that is available to anyone; but is automatically given to married couples.
In the car accident example, my wife can sign for anything, including terminating life support. If I die; my wife gets 100% of what I own. There is no debate from my parents, brothers, ect. The house/business reverts to her, my savings is hers, my stock options are hers.
What you are proposing is that what is automatic for married couples become extraordinary for gay couples. This is what the law intended to overcome. I have no problem with equality; however I do have a problem with either group declaring 'protected' status.
It two homosexuals have the time to "register" there is no excuse for simply signing a health surrogate or inheritence docs.
The inheritence laws you cite are there to protect the production of children for society.
Society rewards the institution, society is not there to reward individuals fetish for a peculiar form of recreational sex.
There is nothing to overcome since homosexuals have always been free to marry members of the opposit sex AND heterosexuals of the same sex have been prohibited from marrying each other.
Homosexuality is only a behavior for recreational sex. period.