What SHOULD they use? The one thing which propogates instantaneously to within our ability to measure it is gravity and the closest thing to a decent explanation of what gravity is, is Ralph Sansbury’s description of gravity and sub-electron particles. The computed necessary speed of a sub-electron particle would get you to one of the near galaxies in a couple of seconds. Anything which anybody with the brains and talent to communicate across cosmic distances would actually use would likely have to involve those kinds of particles.
Is this connected to that pseudoscientific "electric universe" silliness?