I would love to have to add/subtract business days out of the box. I know this can be done with a bunch of conditional checks but it becomes cumbersome. Also have the ability to define what qualifies for a workday. For example, Excel can do this by defining a parameter with 0,0,0,0,0,1,1.
You can define days of the week by parameters 
So each day corresponds to a number 0 to 6 starting with Sunday = 0, Monday =1 and so forth.
If you used the operator ‘:extract’ on a date and choose ‘day’ it returns this number
Yes, I am aware of that. However, if I want to add 4 business days to an existing date but it cannot land on a Friday, Saturday, or Sunday, that is a lot of checking. It would be easier to just say 4 business days and not have to do all of the error checking.