Forgot to mention dimensions. The plan is to go from current 18x7.5 ET49 with 225/40/18 Potenzas to 19x8.5 ET45 with 235/35/R19 PS4S (there is no 19x8.0 option anyway). I think the combination of the extra 10mm of tread and the stickier rubber will make for a big improvement rather appreciated on any powerful FWD. I could already spin the Potenzas on stock power levels so I can definitely find a use for the extra grip with the JB4 on.
In terms of suspension I think there are benefits to be had also by going for that size. The new tire/wheel combo brings the wheels 16.7mm further out from the struts so essentially it's like getting "free" 15mm spacers. I find the current Belvedere wheel to be a bit lost inside the arches when l look from the side but I am not a fun of actual spacers so there's two birds with one shot. Maybe even three, as although I don't think the car really needs any lowering, there is going to be a 5mm arch gap reduction which should look cool and at the same time I win some extra "forgiveness" as the overall ride height goes up 5mm, not bad at all.