Yeah, countries could create extra mechanism to try to minimize discrimination in immigration, taxes, decisions in hospitals, renting/buying a place to live, inheritance, and many other issues that could not come to mind.

Or you could solve it by allowing same sex marriage. That sounds so much easier.

This is strictly my personal opinion, but I would be perfectly fine with renaming marriage to civil union as a whole in terms of law and giving the same rights to all couples independent of sex, leaving the term marriage for other uses outside of law.

However I understand the reasons why people would want to have same sex marriage named as so, I would also be perfectly fine with that.