I would agree with what Prognastat said as well as GCC. In theory, the low fee of getting access to the money is market timing on steroids. What happens if after the introductory period (say 15 months or so) the market has declined further than when you originally took the money out? You would then be forced to sell at an even steeper discount.
My plan once I FIRE is in the case of a prolonged downturn is to cut expenses to the core minimum (i.e. no travel, discretionary, etc.) and if it continues to be painful, supplement some income with potential side hustles/part time gigs (barista, tutoring, gig economy, daily manual labor, even donating plasma) would all help damped the blow to the portfolio and increase its survival rate.