I need to turn the G-System's effects on and off via midi CC's from my DAW. Is that possible?
No, unfortunately the G-System's effects blocks cannot be switched on and off via MIDI CC.
The only parameters that can be assigned to MIDI CC are encoders 1,2 and 3. You can assign them to control a specific effect parameter such as delay mix, or reverb decay, but not to the effect BYPASS.