The FMS has a GPS (with RAIM) as its primary source and VOR/DME, DME/DME with VPU monitoring as secondary.
I accept the limitations of single fit FMS that are not approved to fly approaches, and rightly so.
My question is, does that mean it cannot be coupled to the autopilot?
My opinion is that if I am using the ADF as the primary source of navigation data, what the AFCS is selected to is irrelevant, as long as the aircraft is tracking within the NPA tolerances.