The state shouldn't be getting into the marriage business. And where there are benefits not related to the "holy" or contractual aspects of the union (inheritance, property rights, etc) lets make it equal. Let a church decide if it will marry someone, but let all the other stuff be equal beyond that.
Spousal immunity is the result of thousands of years of social tradition being codified into law.
You could end government issued marriage licenses, but, only if you abolish spousal immunity, or heavily regulate it [ie have the state decide whom really is, and isn't "married."]
Are you for abolishing spousal immunity?