My personal answer would be that commands (as defined as "things the issuer cares about the response to") don't belong on message busses, and there's probably an architectural mismatch somewhere. Message busses are at their best when everything is unidirectional and has no loops. If you need loops, and you often do, you're better off with something that is designed around that paradigm. To the extent that it scales poorly, well, yeah. You ask for more, it costs more. But probably less than trying to bang it on to an architecture where it doesn't belong.

You want something more like a service registry like zookeeper for that, where you can obtain a destination for service and speak to it directly. You'll need to wrap other error handling around it, of course, but that almost goes without saying.