My sneaking suspicion is 'not a great deal' but I was hoping someone knew what current weight vs capability was. My own experience with advanced targeting pods would suggest that even if you got to 40Kg you could carry the front fifth of a Sniper...which seems to lack utility...
A lot of that 40Kg could be down to the flight loads it would see on the type of platform on which it flew. Given the benign conditions in which Zephyr operates, a lot of material might be removed or replaced with lighter alternatives.