Discounts - Stack or Not Stack Ability

I used discount codes for different length of stays to offer discounts for 10, 20, 28 or night stays etc. and prevent multiple discounts applying to a single quote by using the number of nights criteria.

However, with 26 rentals I have started doing flash sales for specific properties that may need a boost in the booking department.

The problem is I have to modify existing length of stay discounts to remove the property that is subject of the flash sale otherwise there will be multiple discounts.

My thought was to create a SUPER DISCOUNT FLAG, when a discount has this flag set no other discounts can apply.