@Cory Weiner not sure if its the most efficient, but if it's a suitelet you can return the csv on the submit button on post request. if not, you can call the suitelet via a ue/cs button and return the suitelet as a csv response. that's how i'd do it

I've done this exact thing w/ a suitelet w/ a button on it that generates the CSV from the selected items on the sublist and lets the user download it. Definitely a way to do it.