I really like this idea, Benjamin. It seems like a much simpler solution than trying to rig more hardware or switch MCU's.

However, I'm guessing that there might be an issue involved with the actual message provider. Unless the device at the other end of the modem connection is in an always-looping server-type mode, then requests from the display device would be purposeless. I'm just guessing here, but if the message sender is only in a "send" mode, and does so at 30 minute intervals, then unless the modem has a non-volatile buffer for the last received message, then we are in the same boat as before.

So, if this is the case, it would only take some easy software changes on the message-host side as well as some very simple software changes on the message-client side. I would say this is an optimal solution, so long as the message host device is accessible by the developer.