Airbnb, I have these same needs.
(1) Please make a setting that prohibits checking out on certain days, such as "block checkout on X day of the week" or "only allow checkout on X,Y,Z days of the week." It seems that would be very simple to program.
(2) Please also make a setting that specifies which days of the week must be booked together (e.g. "if X then Y" AND "if Y then X", or "X and Y cannot be split")?
Note: I *would* be willing to make an exception to the above rules and let someone check out on a Satuday, *as long as* it were a 3-day minimum booking (I would usually make more $ for a Wed & Thurs combined as I would for a Saturday). So if you were getting fancy, perhaps you could consider making a conditional setting like "only split X&Y if condition 'Z minimum number of days' is met".
Thanks!