[ibash]

Marriage is a social construct. Strip away how everyone else views it for a moment and look at it in a different light: If there were no tax benefits, no immigration benefits, etc - would you be the person's partner anyway?

If so, get married for the visa, it doesn't change anything important anyway.

Incidentally this is what me and my wife did so we wouldn't have to deal with the immigration lottery, it's working for us.