I would also appreciate this feature. It's more common that I'll want to waive the odd minimum here and there than that I would want to increase the minimum here and there.
One situation is what OP describes, where you don't care as much about meeting a minimum when the dates are fast approaching with no bookings.
In another situation, I currently have a guest checking out on Friday and a new guest checking in on Monday. Because I require one night in between reservations, this means that Saturday night is free, but Friday night and Sunday night are not. Saturday night shows on my calendar as available, but it's impossible for anyone to book it because they can't meet my 2-night minimum.
I would gladly accept a 1-night guest to fill this slot on my calendar, but I don't want to have to set my entire calendar to 1 night by default and then have to log in every single day to update the minimum on every day manually to 2 nights as it comes into my 3-month booking window...or else risk people booking 1-night stays 3 months out that I wasn't able to prevent by updating my minimum on those days in time. It would be far easier to just be able to click this day and change the minimum to just one night, just like I can change the price for one night.