there is a windows project called "astrophotography tool" (APT) which does just what you described. Guiding is det manuelly at the handbox or by means of a dedicated windows app. Once up and running the connection is closed and the APT software takes over and coordinates dithering inbetween frames.
APT shows a guinding graph so there must be some comunication with the MGEN guider. So it seems the protocol supports getting at the data while guiding is running.