Ability to have a sign on/off list for Alerts

It would be nice to have the ability to keep employees on the list for alerts even if nothing is selected, instead of having to add them back every time and do the fill search similar to a sign on/off list. We have locations where there is an on-call supervisor that fills in on a weekly basis and the supervisors only want to receive alerts the week they are on call. Right now, when you remove someone one, they disappear from the list of those that can get an alert. To take a step further would be the ability to put this on a schedule.