The problem with that game, is the draw distance is very bad, and I don't even think there are any costom mods for Urban Chaos that add new models.
The only mod I see for it is a simple AI upscale mod.
https://www.moddb.com/games/urban-chaos/addonsIn order for the game to be a good candidate one would need to reverse engineer all of the archives in the game and be able to rebuild them for one to be able to change anything. Then you have to research how the model formats are and how to create and export new content for it. As a modder myself I can tell you it is a lot of work that normally requires a huge community behind to do something like that. Sure we are already seeing ways to replace or add new models into Dreamcast games made with Katana SDK made by a few people. But the appeal of Windows CE games and mods means there needs to be a whole foundation to mod first of all. Half-Life is a wildly popular game with tons of mods for it. This is why modding HLDC is such a breeze.
I think we may be better off doing like others have suggested, modding GTA 2 with camera perspective mods. Or, like I think is more plausible, porting Driver 2 over since it is a PSX game that would allow for much more expandability on the Dreamcast and source code was just reverse engineered for it not too long ago. Pushing that game further on DC with more detailed car models would be a great thing to see. Plus now the developers have fully converted Driver 1 maps and brought them over to that game too. So it can have those as well as all new maps made form those assets. Driver car physics were some of the best around especially for that time.