For various reasons, I've pretty commonly ran in to situations where I would've wanted to know what internet ID and IP addresses a computer had previously connected with. It would be nice to be able to log connection information from computers, even if it was just to a flat-file.
Some of the information in the host log is useful, but unfortunately it's stored on the host which makes it useless if the host isn't online which is often why I;ve wanted access to the information. To see some logging similar to this on the server would be a good start. It'd also be nice to be able to set clients and servers up so that client logs were automatically uploaded to the server when a connection was established but that's honestly probably less important.