Shane,
Great idea! Using an exfiltration outlet is a good option when the pump rate is constant. It actually saves the hassle of entering a multi-point stage-dischrage curve as required by the special outlet. Just enter the constant CFS rate, and set the invert elevation to the level where the pump will turn on.
To avoid confusion, be sure to change the device name from "Exfiltration" to something more appropriate, such as "Pump". Since an exfiltration outlflow is normally discarded, you will probably want to change the device routing to Primary or Secondary, depending on how the flow is being combined with other outlets, such as an overflow.