The chip's phase measurement transer function has a positive slope for phase
angles less than 0deg and a negative slope for phase angles greater than
0deg. So it seems to me that resolving the 180 deg ambiguity is just a matter
of knowing which slope you're on. This might be done by switching in
a small known reactive component

You can do this with an MFJ or any other analyzer to resolve the sign ambiguity
of X. Switch in small known reactance, see which way X goes. Also, hooking a
computer interface to an MFJ would probably not be that much more difficult
than interfacing with the AD chip. So, no I don't think this would run rings
around an MFJ. However, if you do go this route, I would be very interested in
how it turns out.
73 Gary N4AST