DS has been its own luxry brand since 2015, so maybe this is them trying to really show they're not just Citroën anymore. Licensing stuff could also be a reason.
Sometimes car companies want their in-game branding to match what they're doing in real life.
Totally makes sense about the 1500rpm rev. I was starting to think it was just the engine warming up or something. But yeah, those vibrations when coasting or slowing down? Definetely messing with my head. I’ll take a look at the engine mounts like you suggested, and maybe check out another DS7...