Vehicle customisation and Rideout Customs
Rockstar has now shown the garage, the lift and the finished cars. Customisation is in, and the press set is the proof.

Vehicle customisation was one of the larger open questions about Grand Theft Auto 6. Los Santos Customs and the Benny's shops were central to Grand Theft Auto V and its online mode, but Rockstar had not shown an equivalent.
The Ultimate Edition press material shows one: Rideout Customs, across three images.
What the three shots establish
The first is a finished build under studio lighting, a gold lowrider sitting on spoked wheels with playing-card detailing on the centres. The second is an interior detail, a red buttoned cabin with a chain steering wheel. The third is the workshop itself, a yellow car up on stands with one mechanic underneath it and another working from a clipboard.

Taken together that is a shop, a process and an output, which is about as clear as it gets without Rockstar saying the word.
The lowrider is a specific choice
A gold lowrider on wire wheels with card-suit detailing is not a generic tuner build. It sits in a real and highly developed American car culture, and Rockstar has been here before with the Benny's Original Motor Works content that became some of the most popular material in Grand Theft Auto Online.
The green Canis off-roader shown elsewhere in the same press set, under the name One-Eyed Willie, points the same way from the opposite direction: a heavily modified 4x4 photographed in a workshop mid-build.

Why it matters more this time
Under the evidence system, your vehicle is a tracked item that the police match against you. That puts customisation in an awkward and interesting position: the more distinctive your car, the easier it is to describe.
A resprayed car has historically been the way to clear a wanted level in this series. If the police are now working from a full description rather than a star rating, a visit to a body shop stops being a cheat and starts being evidence disposal.
What is not known
Rockstar has not described the customisation system, published a parts list, said whether Rideout Customs is one shop or a chain, or confirmed whether respraying interacts with the wanted system at all. Everything above is read off photographs.
