Every ounce you have in the hubs that don't float on the suspension reduces certain suspension attributes. You end up with a crappier ride and poor performance.
I see no reason the small motors can't be mounted inboard from the wheels on the underside of the chassis, as are a rear differential or front transaxle in an ICE car.
Having such a small and lightweight power package opens up serious design and performance opportunities. Plus, even without major redesign to take full advantage, every reduction in weight rolls through the system, providing immediate improved acceleration, cornering, & braking or similar performance using smaller tires, brakes etc..
Although, I guess at some point in the future if we can get the weight down low enough and the strength of the motor high enough we could replace the existing braking system with a motor for the same weight penalty we already pay.
In an ideal world all the energy from breaking would be used for regen anyway.
I'm not sure how close we are to that but it's an interesting thought experiment thinking about the trade offs we might be able to make in future.
EDIT: Quick maths show that decelerating at 1g (basically what the best sport tires can do) in a 2000kg car at 300kph requires absorbing ~1500kw, so conveniently two of these motors.
Unless you used the motors to power fans instead, then you could use that for downforce and propulsion, and get well belown 2 seconds, theoretically.
F1 cars with fans to run them upsidedown but with remote drivers for their safety maybe?
