HAM sets are fine. If voice transmission, why not Dakota? It worked before, right?
Sending videos with ASL is another, since there are not that many paid interpreters, and how many hours will that tie up?
Using Pictish characters works, since there are variations in characters, and in longitudinal directions, which change meanings.
Sir Arthur Conan Doyle’s ‘stick men’ might work.
Galileo used to make his journal entries in reverse. Let’s have fun, and use any system that might be mentioned, with the old “plus-1, plus-2”, AND in reverse!
I think they call it Lakota.