Of course the weight of the DCDC to get to 2 kV will have a weight. It must also be in close proximity to the panels. This will be quite difficult in a soft kite scenario.
I found this, 1200 V DCDC capable of 250 kW peak at 30 kg. Expect a weight for a optimized unit for 1 MW to be around 200-300 kg. [guesstimate]. Much lighter than the cable