Hey
for that high power , the best solution IMHO is very big resistor , with say 150W load in A control loop ,
the electronic load will keep constant current , until the resistor warm up , then the resistor is warming hence voltage drop thus lower current right ? . well , the CC is going to dissipate less power in order to "move" the required power to the resistor , 150W is easy , safe and cheap , you can either buy or get for free one of those 2000W heaters ( fan cooled ) , open it up , hack it in order to be one huge resistor ( depending on your load ) , if 1 Ohm needed , cut it every 7 Ohm or so , you'll get 7 resistors , parallel them up and you have got 2KW 1Ohm resistor
, you may want 0.12 Ohm right ? (100A 12 V ) , well , 20 pieces of 2.4Ohm is going to do the trick
It is going to be very course , Hence if you need like 1~5 % accuracy , add some active load to react in order to draw the necessary current ,
that is my take on crazy ass KW loads , I hope someone will find it helpful
Cheers