Should I use WordPress for a static site?
From business perspective this question is silly at this point in the design process. All you’ll end up doing is wasting time (money) now.
Whether you should use CMS or not should have been ironed out before design process started. And should have been included in project requirements.
The site is basically some typical brochureware with maybe 10-15 pages.
Plain HTML/CSS + JS (if necessary)… hand over the project and be done with it. Don’t contemplate any further.