Hmmm, very interesting project, i used to fly a little control line'back in the day' but nothing quite on the scale of this project.
I think your friend is going to have to accept that some of his wish list is unachievable. Flight time and weight are probably the first victims of harsh reality.
The two fans combined draw 250 Amps so to supply them at full power for 6 minutes would need at least a 10s 25,000mAh battery.. that would be five of these: http://www.hobbyking.com/hobbyking/s...Lipo_Pack.html
Not only would those batteries cost close on $900 but they would be enormous and weigh 16lb for the batteries alone!
More realistically you would be limited to a maximum of two of those batteries for a total mAh capacity of 10,000. That would give you about two minutes flying flat out. Weight is still quite high at over 6lb for the batteries, which means you are at 10lb just for the power system before you even add an airframe. The final flying weight is going to be around 20lb, maybe more.
You would need two high voltage ESC's capable of at least 125Amps, preferably a bit more, such as: http://www.hobbyking.com/hobbyking/s...ler_OPTO_.html
The practicality of flying a 20lb very high speed control line model needs to be considered. The control lines would need some form of anchoring to the ground as no human would be strong enough to hold the centripetal forces generated. A quick calc tells me that at 100mph the 'pull' on the lines would be about 190lb and if you could do 200mph then the pull would increase to 760lb