The module already has the option to display the notification of INDOOR_TEMPERATURE by other modules. People also have outdoor sensors. So adding the functioncality for showOutdoorTemperature (assuming the notification OUTDOOR_TEMPERATURE is already existant.
This could then optionally replace or complement the outdoor temperature received by the weather provider.

After this https://github.com/splattner/MMM-MQTT-Notification could be used to send the notificaton if using MQTT.