That's why instead of an M3 I got a Boss 302 AND a BRZ Limited.
The only things I did to my 302 are fluids and the MGW shifter. I haven't driven a GT with Track Pack in a track environment but the Boss suspension settles quickly without affair. I had a very fast friend who's used to Miatas drive my car in an autocross and he posted some very fast numbers. Goes to show if you can drive a Miata fast you can drive anything fast! I think the biggest hurdle for a newb track driver is that if you go deep into a corner and brake too abruptly the chassis will take considerably longer to settle (the BRZ/a Miata will do the same to a lesser degree) due to weight. I think at the end of the day the involvement in the Boss is pretty good though not quite BRZ/Miata/S2K) levels. If anything the driving position/seat height of the Mustang platform could be much better. Hopefully the upcoming S550 platform addresses this issue.
The things I prefer in my Boss are (surprise!) the superior sound deadening on a longer trip (this may be a factor of just being a larger car) and man I love those Recaro seats. I'm 5'9" and 175 lbs but they hold me so much better than the BRZ seats while also being much more comfortable. From a driving perspective of course it's the ease of torque steer. It only took one event to learn torque steer properly since the power is so accessible. And of course the sound with the trackey and lopey idle, haha. Hard to beat that sound of an American V8 winding to 7500 RPMs.
Good writeup!