In the Saints Row games, you could unlock the cars and outfits of enemy gangs and other factions after defeating them.
In Cyberpunk 2077, I would have loved to unlock the cars of NightCity gangs and corporations. Alongside special outfits and other clothing options. We have a few, for sure, but it could have been more.
And no, I don't wanna hear about mods, I'm speaking about the base game itself. Something available to everyone, not just PC.