On top of the current 1M, I'd want to see:
Much more supportive seats that can also go down lower.
Better tyres, it's cheap of BMW to have stuck with Pilot sports when PSS were already out, don't care the reason behind it, BMW were just cheap. This car needs more traction.
Better intercooler than the donor car
Different intake so you can hear it!
Track oriented performance parts as an option. I'd like the option to be able to spec the car up to have Pilot Cup tyres, better brake pads, louder exhaust, racing harness, etc, kinda like a GT3 but as options.
Either way, BMW are on a winning formula, there's a strong demand for cars like these, it's only going to get better.