Christ,
So we should allow marriage to be completely redefined, taken from it's roots that stretch back beyond history, so that criminal gays won't be compelled to testify against each other.
And you think it is worth it?
The fifth ammendment was just one example. There are other privileges given by marriage that are not covered by civil unions, living wills and other contracts. Furthermore, you are assuming that anyone who invokes the fifth is a criminal, bringing into question whether it should be an ammendment. Also, appeals to tradition are a logical fallacy. Plenty of things were done for a long time and were later acknowledged to be unjust.