You are the expert on the requirements and design for your application, which, as I recall, is autocross/gymkhana contests. I would think that total agility contests like that would favor a level car, as you say.
I qualify my opinion that the rake is for high speed stability as just that, an opinion. I based it initially on these points:
My ETC came with the rake. The car was exactly on the ride height specifications in the FSM (with new tires) throughout its life.
My ETC did not come with a spoiler. I don't believe that a factory RPO spoiler was available for the 1997 ETC.
The owner's manual states "This car will go 150 mph." Car & Driver timed a 1997 ETC (I believe, it might have been an STS) at 145 mph on their home test track, which has a good straightaway but is not suitable for testing top speed of very fast cars.
I'm not at all sure that the ETC body style would be stable above 120 mph without the rake; this is, of course, yet another opinion.
The ETC/STS (VIN "9" cars) designed to run with the big dogs on the Autobahn, and the VIN "Y" cars were designed to keep up with traffic (up to 120 mph or 195 kph) . This is from the car trade mags of the time.
The throttle response and stability at 100++ certainly supports real-world long-distance driving at those speeds, while dealing with similar-speed traffic and real-world roads that are designed to support such traffic. So says a friend.
Now, if I had one to test, and had wheel height sensors available in real time with output available for recording, I could verify the utility of the rake in keeping reasonable weight on all four wheels at speed. Wheel height, with spring rate, translates into weight on the wheel, a point that is used in the PCM/PZM/BCM in traction control and electronic stability control.