Same as the delay time for units but instead of the option to set a time delay for staff availability. In reality we won't always have someone at a firehouse or emergency squad so maybe have a time setting that allows staff to pop up within minutes, seconds or even random time patterns then our units can go out.
For example. Say I wanna send an Engine and Truck out and I would need atleast 6 members for each truck. I'd have to wait until 12 members arrive to my fire station.
With that said, Even the thought of having a new building, Houses. That you can set your members at and when a call comes they can go from those houses to your stations.
This would be optional btw. Not all members may want these options but it would bring out more of a challenge and time response delays.
These House buildings could cost 500 credits or so as there would be a lot of them built. Place up to 5 members maybe more and have a person icon or vehicle icon that shows them responding to your station then your unit can go out once the unit is fully staffed.