This is somewhat shocking to read, as I am developing a technique that goes off of this very idea. I have begun looking at all the events and people in my dreams, and tracing them to the time of day and activity I was doing the day before to find patterns. I do believe it is possible to discover the mind state and type of activity one must be doing to implant them later in your dream. If this can be perfected, a person could implant a series of events or a consistent dream sign every day, and reach very consistent lucidity. Still developing it, alas...