Why not 4 calipers up front?

Hydroboost doesn't improve braking or stopping distance, it just makes the pedal easier to push. Just like any power braking system.

Drift cars have a 2nd caliper in the back because they work them independently. The primary caliper works like your normal rear disk brakes and is hooked into all 4 wheels. The 2nd caliper is operated off a completely separate system, plumbed independently from the 4 wheel braking system, so the rear wheels can be locked up without any brakes on in the front. They're usually actuated with a hand lever. Basically doing an e-brake slide but with a lot more control and precision.

As for a second set of rotors, just get bigger calipers and pads. Adding a second set of rotors would just add a ton of weight, plus the complications from plumbing them. And as AJ pointed out you still need to have the tire and the traction to make it worthwhile. You'd be far better off adding a 4 or 6 piston aftermarket caliper with larger pads.