All-wheel drive sucks. The front wheels steer, the back wheels go, and that's the best way to get it done. The only advantage AWD gives you is during the launch and in adverse conditions. It adds weight and understeer.
I would agree, because it's true, that in perfect situations a Front-Midship engine placement with rear-wheel drive and a rear transaxle or a MR setup with a rear transaxle would be the best for overall weight distribution and handling, respectively. If you want great transitional response, a 50/50% front-rear distribution is best. f you want the best straight-line braking performance it's best to have a slightly rearward weight bias, such as in a Viper, Z06, 599 (which I guarantee will brake well), and even a ~60% rear bias will work phenominally. Porsche's 997 911 has the same sized front and rear brakes. About 60% of the car's mass is on the rear axle, and therefore when the brakes are applied the weight shifts forward and ends up with a closer-to-50/50 distribution than a FR or FF setup, which means the front and rear wheels can take a similar amount of brake pressure and distribute the load fairly equally between all four wheels. A mid-engined car creates this same effect.
If you want to accelerate quickly AWD is usually the best option. Most AWD cars can handle a drop-clutch launch from high RPM, and therefore can rocket forward. A 911 can nearly match that because so much weight shifts over the rear wheels, squishing them with authority. But RR isn't the best for overall handling, because the rear end wants to swing around during low throttle situations, and the front end, for lack of weight, always wants to understeer. Only Porsche's technology and great engineering have overcome these characteristics, and they don't have it quite right yet.
Obviously FF caers don't do anything well, so we'll skip them.
I guess my point is that front-engined AWD cars have too much understeer, though they launch well, and the system just adds too much weight to a mid-engined car to make use of the weight distribution benenfit.
If AWD with a mid-engine setup was the best, this here Cayman GTR would be that. It's not. And yes, they could splice in a Turbo AWD system.