Electronically programmable buck converter module
On the face of it, it might work but also, because of parasitic capacitances in the digipot, it might turn the regulator into an oscillator or it might produce a much degraded load transient response.

A better way might be to make a high side variable constant current source and supply a small additional current into R2. This will make the chip regulate at a lower voltage. In fact, if you put a diode in series with R1 you should be able to regulate down to nearly 0 volts.