“Why don’t we make every man and woman sign a legal document before getting married that they commit to giving/accepting a get (subject to Beis Dins agreement)”
The chasson already stupulates under the chuppa that he is marrying the woman subject to “das moshe viyisroel”. this statement is witnessed often by several hundred people, including two who are designated as witnesses specifically by the chosson. I wonder when a beis din with some teeth (sadly, there is no such beis din which has given rise to the questionable practices of prenups, etc) would tell either party, you are not acting in accordance with “das moshe viyisroel” and we are going to annul your kiddushin retroactively since you violated the condition. that would create quite a stir, but sometimes you gotta do what you gotta do.