Chat protocols are Fun Things to Hack Together, and have some thorny issues that are interesting problems in their own right. However, if your goal is to be The New Thing, don't. You will run into all the same issues that other protocols (notably XMPP) have already had to tackle several times with the current status being An Acceptable Tradeoff. If we want a global communication standard, we should focus on XMPP, as the most general, well-defined and decentralised alternative available, with many different implementation both of servers and clients, not to mention a broad range of small, medium, and large servers.