The request seems reasonable considering the history has been to use one or the other. However, can we change it? Can we go back out with a revise RFI/SS Notice to update the NAICS code to 541715 under the guise of increasing competition?
With the 541330 code there were 2 respondents that are potentially capable but until proposals are provided it is unknown.
FAR part 19 addresses NAICS and FAR 19.102(b) answers your question. The NAICS code chosen for any acquisition should reflect what best fits that acquisition. A small business that grows out of a particular NAICS and is no longer considered small business is a common occurrence. Changing the NAICS code is allowable, but only for the intent of ensuring it best fits the acquisition, not for any one given company.
FAR 19.102(b) The contracting officer shall determine the appropriate NAICS code by classifying the product or service being acquired in the one industry that best describes the principal purpose of the supply or service being acquired. Primary consideration is given to the industry descriptions in the U.S. NAICS Manual, the product or service descriptions in the solicitation, the relative value and importance of the components of the requirement making up the end item being procured, and the function of the goods or services being purchased. A procurement is usually classified according to the component that accounts for the greatest percentage of contract value.