Lanturn

Look, it may shock both of you to learn that I have already thought about this.

Not only would we need an Ampharos or at the very least a Chinchou or a Lanturn, we would also need to trust it not to electrocute Watchwing or whatever flyer would be carrying it, or we would need to take it to the top of the radio mast manually and trust it not to fry that, and then we would need it to reproduce a complex series of flashes of precise lengths and timing without any mistakes or else risk garbling, or worse, altering the content of whatever message we wished to send.

All of that sounds possible to me, David.

Of course it's possible, provided that we have three or four months in which to set it up.