I would love to see advanced paint groups for windows so you can paint the rear windows of a car separately like in real life. It looks much more authentic than a full window tint which is not allowed in a lot of countries (it looks cool though!).
It could be split up in three groups:
Group 1: rear windows (behind B-pillar)
Group 2: front side windows (driver and passenger side door windows)
Group 3: front windshield
And while you’re at it, please add windows as paintable Vinyl sections 