I don't know about the "dorifto" cars, but when we install a hydraulic handbrake in the rally cars, it just installs in-line with the rear calipers (Really it's just a master cylinder with a handle attached) when in the "rest" position it allows the fluid a clear flow through the piston, only when activated does it add pressure. to the line and closes all four rear pistons on the fixed calipers.

I don't want to say the drift way is wrong, but that seems like it can cause issues, and perhaps that was just one car you saw? I can't imagine a professional drift team setting up their calipers as dual channel. Maybe because I don't see the logic in doing it.

I like your Idea of swapping the cable for a wheel cylinder, and it should be a pretty easy modification. once again, overkill since a Hyd. handbrake can just activate your standard calipers without the extra work. and no need to run a second line and revisiour.

K-sport sells a nice hydraulic handbrake assembly for $250, (Street price is $187) thyey also sell a line kit with an fittings, but for $135 street price you can do better just buying the inverted flare couplings, some hard line and a bender.

Remember Matt, I'm a Brake and suspension geek.. I learned early that anyone can make a car go by throwing power at the problem, but it's the true geeks that can make a car stop and turn that hold my highest regard.