This ofcourse would not be official I guess. Questioning official, sorry, no one in the world is going to allow this to happen with all the traffic running.
My suggestion, Nice idea for the time trial but make sure that you do it outside traffic areas so that it gets safer especially for those who are'nt participating.
Try using Mangopir road to Hamdard University. The road is slightly bumpy but with not much traffic at all. The cars participating arent Race cars, (they'd mostly be front wheel drives for god sake) so it'd be better to use some tarmac and some not so much B-roads to start with. Road to Hamdard University is ideal for a Time Trial. There'd only be trucks and private taxies tops to worry about. and some clean stretches, bends and turns. The only issue are the speed breakers who aren't found that often but thats where the driver'd test his own skill and the meat under his bonnet in getting away quickly, and thats exactly where time will be gained and lost.
And you're going NNZ so from even Surjani to hamdard you have about 24 KM of tarmac all waiting.
Drive fast yes but safe.
Cheers mates