Extend MasterServer?

Is there a way to extend Unity's MasterServer functionality (I don't mean the remote MasterServer, I'm referring to the MasterServer class in Unity)

From Unity I would like to do the equivalent of

 MasterServerExtended.FindOpponent("myGameType");

Just like I can do:

 MasterServer.RequestHostList("myGameType");

That instead of returning the HostData list returns a single HostData entry for a single opponent (will be the server in a two player game).

I'm pretty sure I've worked out how to extend the remote MasterServer (RakNet on Linux) to accomplish this but I'm at a loss how to do the Unity side of things.

Any ideas?