
Vehicle upgrade “cards” that can be applied to vehicles through a manage menu. Such as a “storage upgrade” you could apply to a go-kart or tricycle, which would then add a trailer behind it for storage, themed/colored the same as the tricycle. Or speed boost that could be used on the trucks to make them faster, etc. These would obviously be late-game. Could also incorporate fun patterns/designs like flames, race stripes, rainbow, etc.

I was about to suggest this too Upgrade vehicle storage!