No offence but this is performance car. Therefore I would make it 300kg ligter, i.e. Porsche Boxter weight.
It would then handle superb and be agile, as well as better accelleration etc. It doesn't need more than 300 bhp
If you want pratical buy a Mondeo....
The only thing I would have done about the practical design of the car is a rear seat, aka Audi TT