Coral, is what you are referring to called "get al tnai" a conditional divorce? I know that during WWII when a relative was in the US Army, he gave his wife a get al tnai in case he wouldn't come back she would be allowed to remarry. It sounds so painfully awful and so beautifully loving all at the same time...
Not a get al tnai, but an actual annulment clause that would retroactively annul the marriage. For example, it would state conditions like as long as she doesn't do XYZ it is valid. So if she does XYZ, she can annul her marriage retroactively and would not need a get in case she asked for it and the husband refused.
