Except for the aerodynamics, the other problems are easily solvable by a little extra hardware and a little extra software. You put four wheel disk brakes (which many performance cars already have), then let the computer decide which two get the most pressure. Then you put four wheel steering, with similar computations. Sure it would add expense, but these things are already going to be phenomenally expensive for a while. The aerodynamics, as I already noted above, are problematic, but not as problematic as it might seem. You only really need a fast back when you're racing, and nobody is racing a self driving car for fun on the weekends. Drag is dependent on speed, and I can't see anyone building a performance car that is autonomous (beside Tesla, but that's an ego thing), because what's the point?