I don't know for certain. But one point to consider is that you have to qualify your “simply” statements with the fact that we are talking about millions of towers and hundreds of millions of repeaters over millions of square miles. While RCS works on top of the backbone that's already there and fallsback to SMS by design. So it might actually be simpler. The big up is that the server is on the carrier, not centralized, which makes it entirely different than what you are talking about and giving it more resilience.