Thus the governement has to have the central role of record keeper."
If we make a distinction between "marriage" and "legal contracts" then we do not need government to annull a marriage. If we let churches handle the marriages, then records are of little to no importance.
"Laws such as inheritance, incompetency, medical surrogacy are all dependent on a consitent and uniform rule of marriage."
I wrote that "[e]ach couple should have its own contract for its specific circumstances. Some couples already do this via pre-nuptial agreements." I wrote this to address the point that you raise. The purpose of the contract is to legally "form a union for the purpose of shared benefits and legal protections" such as those you cited.
"Additionally as a society we reward the insitution not the individual."
I'm a fan of limited government, rather than a state that engages in social engineering, no matter how well intentioned.
You are refereing to cohabitation agreements which already exist. You can just educate people to enter into those "mere contracts" rather than getting married.
As an institution rather than just a contract Marriage is afforded certain priorities that are not available in mere contracts.
For example, despite what a will has, many states have mandatory widow's/widower's shares.
For example, child supoprt would be fixed under a mere contract concept rather than as the cost of living adjusted system now.
Those the want only contracts have been free to do so for decades. cohabitation contracts are readily available from various form companies.
However as a institution marriage as a means of producing and raising children is paramount to the continuation of a society. This is not to be left to the haphazard contracts any more than one would want to privatize the US navy to france.