International sign language

There should be an international sign language, akin to Esperanto but in sign. It would be possible to learn this sign language and then be able to communicate effectively with someone who speaks a different language while also learning their language. Hearing people could speak and teach their own language while learning someone else's language and communicate effectively all at the same time. I've spoken with some deaf people about this who said that in international gatherings of the deaf, for instance at the deaf olympics, that an international language is improvised, but that it's rather basic. It would be so fundamentally awesome for Esperanto to be a sign language that I just wanted to suggest it. How could this happen?