I just want to reiterate: the reason why the current command line tools are slow is because they have to wait for the discovery phase to finish before they can query the desired information. The idea of the daemon is that it is already running before and it has already accumulated the information.
If the command line tool wants to use the ROS interface to request information from the daemon it again needs to wait for the discovery phase to finish before it can do so. It might only need to wait for the availability of that daemon but still this implies a significant overhead in waiting time for the user. I don’t think a command line tool (which e.g. is often also used for completion) can have that time penalty. While I am certainly not a big fan of having a different transport mechanism I don’t see how the requirement of the lowest latency possible can be fulfilled with using a distributed peer-to-peer system like DDS.