A easy and cheap way to do this: Simply transmit different subaudible CTCSS (aka "PL") tones under each type of report. For example, the current regional forecast would be accompanied with 67.0 Hz, marine forecast with 69.3 Hz, degree-day statistics with 71.9 Hz, weather warnings with 100.0 Hz (in addition to the old SAME codes), etc. There are 42 standard tone frequencies to choose from. This would allow new receivers to record the most recent broadcast in each category into a separate audio file in flash memory, then play specific information back on demand -- while the older receivers would continue to work as they always have.