I think there should be a list nick function for the new version of mirc as there already has /list *channel*.
What would this do, list all the nicks on the network...channel? Or would it just list the nicks that match a pattern? If that is the case, /who
already does that, match a pattern, and channel too. If ya wanna list all the nicks on the network, that would take a long time, and i dont know if IRC servers do that, list all the nicks connected to it.