I have tried this in the past and if the rule set allows you to do it, I haven't figured out how.
Instead I started blocking of certain days in the calendar manually so that all my guests were forced to stay only 4 days.
In your case, I am wondering if blocking off Fridays and Mondays (with a minimum if 2 day stay) it will bring you a desired uniformity; it will always leave a day in between guests and eliminates the back-to-back single stays (aka too much cleaning). You can always say - "Minimum stay 4 days during weekdays". I am assuming you are not on IB.
I have changed my mind about hosting over the years; today I rather only book the amount that keeps it fun, because 'happiness is worth every penny'. I no longer feel I am loosing something when it is not booked.