Buck-converter dynamic output-voltage using digital-potentiometer
Are there any concerns with this method, or better yet, is there a
  better way to achieve this output?


Any kind of DC DC converter need a way to stabilize it's voltage and has a feedback loop, usually a voltage feedback loop. The loop needs to be stable to prevent oscillations (ripple) and also to prevent the voltage from dropping out. The loop also needs to be able to appear as a low impedance source. Not all converters (and their components ) can work across all voltage ranges. I only understand the basics, and can use tools to help me stabilize the loops (multiple semesters of courses can be dedicated to power control and switchers) 


One method I am currently about to test is the LT8390, which markets itself as an adjustable DC DC conveter. The range also checks out in the tool, and you can use a current DAC to adjust the feedback loop.