I think I totally agree with you about the best way to seriously track a car. That is, buy or build a race car. But I would have thought that your examples (CS and GT3RS) are pretty different than a normal street-track car, including the NSX. It was my understanding that the Porsche, in particular, holds up well to track use. I think the turning point, and perhaps your reference to a cup car, comes from a full cage. That is the safety point that seems to offer some serious benefit and also makes a car useless for the street.
The RS holds up very well to track use and mine actually has a cage and I use it solely on the street, in fact just returned from a 1300 mile road trip from IA to AZ and found it to be very livable. With that said if you want an RS to be competitive on the track then you still need to swap parts, most folks add full monoball suspensions, motons, steel brake vs. PCCB's, lighter wheels, track only tires, etc., etc. And all of this takes the car to track only duty as far as I'm concerned, and is exactly why I came up with my "tool for the job" outlook, as adding and changing all of this is a huge PITA and I'd rather have a purpose built car that I can stuff in a trailer, take to the track, stuff back in the trailer and forget about it until next time.
The CS, well that's another story entirely. It's actually quite a cost prohibitive proposition to take to the track. With $40K brakes, $3K Ti coil springs that like to break, and single use ball joints (from the factory) it simply doesn't make financial sense to track that car. You can have a spec miata with full safety, tires for the season and maybe even the truck and trailer for a set of a brakes on the Fiat. It is very well suited for a fun drive down highway 1 though, and makes a great noise doing so.
I guess my point was not about serious tracking. It was about casual tracking. I believe that is a more responsible way to experience a sports car than "canyon carving," which implies driving well over legal limits for fun. You may decide to do that and I probably would too if I lived somewhere it were possible, but it is hard to construe that as responsible as casual tracking. And I think that casual tracking has to be part of what a manufacturer intends when it designs a sports car.
I understand your point and might have even fit the description in your minds eye back when I was 19 or so, riding my sportbikes with nothing more than a pair of Oakley's and flip-flops, but then I grew up, gained a certain measure of mortality and now I have just as much fun out with other enthusiasts for a weekend jaunt through the mountains, canyons or whatever fun roads we can find at a reasonable and legal clip. And to reiterate that's where I find the NSX to be absolutely sublime, even better than the other iron (and carbon) that sits in the garage next to it. I find that turning the car into something else doesn't always make it better, but again it's just my .02 and worth exactly what you paid for it
But regarding the subject of this thread, I value and appreciate your suggestion regarding the BCs. My own NSX will only be casually tracked, and even that may be a bit in the future as I destroyed my last NSX in a track incident. In my case, I would like a suspension that allows for control over ride height and a more comfortable ride than the Koni shocks I have now. My only hesitation with the BC is some talk of limited droop potentially impacting the ride.
Enjoy your X the way it makes you happy, we're not all looking for the same thing and we should all extract every ounce of fun out of these great cars that we can. And an interesting tid-bit on the BC/Swift set-up - I had it installed at SOS and I could see the odd look on the tech's face when he opened up the box and saw what I had provided, but he was kind enough not to say anything at that time. Fast forward 6 hours once everything had been installed, aligned and dialed in once I came to pick the car up. The guys handed me my old set-up and were talking about how surprised they were with the suspension and that they had fully expected a less than pleasing result. After chatting a bit we all agreed that the Swift spring option really brings out the best in this particular set-up. They also asked me what other option I had considered and when I told them Moton's they asked me "why"? My point exactly, as I would not see any benefit over the BC's whatsoever for my intended use of the car, just as I wouldn't see any difference with any of the KW, Bilstein, Fox or other variants either.
Honcho - found the same to be true about the BC's after about 1K street/fun miles. And excellent rest of your post. I found that driving instructors and schools are worth their weight in gold vs. the same money spent on parts without the skill.