There are some flexibility features I'd like to see with the late penalty. The ability to have a "grace period", where there are no points deducted after the deadline for a period of time determined by a chosen date/hour.
Right now, after implementing a late penalty, there is no option to skip weekends or holidays. Having the flexibility of skipping holidays and weekends, and having the penalty continue again on Monday would be amazing. (If the student hasn't turned it in and is at -10% on Friday, it stays -10% through the weekend and picks up at -15% on Monday)
As far as functionality for these features, I was thinking that having a calendar where you select the days you want the penalty applied would help with the flexbility of having a grace period as well as skip weekends/holidays.