I would like to add an spoiler on the bottom rear window like this:
Rear wheels fairings will be interesting, but the aesthetic impact will be to big.
Maybe the deflectors in front of the wheels will be modified so the air will directed sidewards, so the air will hit the deflector in a 45 - 30 degrees.
30 mm lower body will be also nice, but I am happy with the current setting of the suspension and I would not like to change it...
The bonnet is too short so the wipers are not protected. The Opel Astra G was much better designed regarding this topic. I wonder if there is an bonnet extensions aftermarket.