It is possible - and some carriers do, have the avionics wired to allow any one FCC to simultaneously supply both a flight director and autopilot input. Under this arrangement flight directors remain available even with all three autopilots engaged during an approach. Muddies the waters a bit for BMI170 but serves to illustrate that it's a challenge to get a handle on the the auto flight system of the 76. I never cared for it . The big picture is represented by a mickey mouse virtual reality nav display cluttered to the point of being worthless. Worst of all, the 76 only has two engines
Rant over!