Hall effect sensors work fairly simply. There's a square (or rectangle) of sensing material inside. The power supply connects across opposite sides, and a small current flows.
Depending on the sensor, there may be one or two sense terminals connected to the other two sides of the sensor. When you bring a magnet near, the electric current is forced to travel through a curved path due to the magnatism. This brings the current closer to one side of the sensor, which causes a voltage to appear on one of the sense terminals.
Now, in theory, it'd be possible to simulate this with potentiometers, but I'm not sure how many terminals the sensors on the DC controller have. If there's a single terminal, then you might be able to use the pot as a voltage divider. You might need a couple of resistors to reduce the voltage swing on the pot though, as the sensors may not output rail to rail voltages.