What's wrong with its current location? This is a pretty standard location for many vehicles.
Leaving an OBD dongle in the port after shutting an i3 down will sound the burglar alarm eventually by default. This behavior can be changed using something like BimmerCode to change the value of a parameter that controls this behavior. However, that's a bit less secure and might result in a greater 12 V vampire load with a dongle always in the port, especially if it's broadcasting an Ethernet or Bluetooth signal.
2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE