Having thicker anti sway bars in Volvo 240, XC60, and VW Passat have yielded improvements that appeal to me. Somehow I suspect Polestar uses stock S60 anti sway bars like first generation T-5R.You will never completely remove body roll. If you truly want to upgrade the handling, get some KW coilovers and throw away your sway bars.
I don't know about nothing, but it's really good out of the box. I definitely agree about not touching the Ohlins dampers, they are better than anything you'll get from KW (does anyone know what the spring rates are on the KWs?). Same goes for the springs, unless Polestar comes out with a set that drops the car a touch. I wouldn't mind the front sitting about 10mm lower, but that's strictly a looks thing and has nothing to do with performance. A stiffer rear bar could eliminate that little bit of understeer that ultimately shows up in long corners and could give a litter crisper turn-in.The suspension on a P needs nothing. KW coil overs would be a down grade, the ride would be less compliant and harsher with no handling benefit. The only advantage would be adjustability of ride height. The suspension as set up by Polestar is the biggest asset of the car, why would you want to mess with that?