Hi,
You mean take over the function of the voltage reference diode?
Yes that seems reasonable, but i have to say that i havent tried this yet, and keep in mind that when you do that you take control over the entire output, and that means the voltage reference will depend on measurements made with the A to D on the micro, so it will be in effect still in the feedback loop. That is, the micro makes a measurement, determines if it is above or below the set point, then adjusts the 'voltage reference', then makes another measurement, makes another determination, then adjust again. So it's a non stop measurement and control scenario where the micro does all the measurement and control.
This would be in any case, except maybe with the pot, because with the digital pot the circuit would work on it's own even if the micro does not do any more measurement, as long as the initial setting was right or at least close (like a hand turning the pot, then letting go).
So it's up to you what you want to try, and test fully. Maybe try both ways if you have the time and have any digital pots around.