The only advantage of setting off in pairs would allow for a larger amount of riders to enter, but I dont think that is what the organisers want anyway.
With regards to the safety aspect of it, It is happening now anyway! How many times do we see riders circulating together, or pulling out of the pits together to blast off down Bray Hill.
I have some pictures I took at Ginger Hall of the second lap of the Superbike race that shows how close they are riding next to each other. I will post them tonight.