Car Model Modification Code

So me and my cousin have a bit of an inside joke that started on GTA V. When I was looking at Seatown's cars in-game, I immediately thought of the joke.
My request is more of a question to begin with - unless it can be done.
What I want is a code to change the Seatown cars' models to that similar to a Prius. If this impossible in code form (and I doubt it is), what about a Dolphin or disc patch for a "mod menu" to activate Prius cars?

If you've got any thought on this, please let me know.

P.S.: Yes, I'm a bit of a n00b, but I'm also optimistic

Very difficult thing you're talking about and I highly doubt it can be done. I've seen it done in GTA games with spaceships and shit, but the Wii doesn't have a way to model objects like the PC does.

This is possible.

The question is, where the game stores the object textures. As far as I know, every map is defined in an own .ff file and in there it says which files are loaded so you need to find their locations in the ISO or without that information.

Extract, modify and re-import then using a program like Trucha Signer to manage the ISO files first of all.

@Bully

Is there a program to modify objects for Wii games? There must be, because look at such game bootlegs (or whatever they're called) like Mario Kart Black. However, maybe the program that was used to re-create Mario Kart Wii is maybe only for Mario kart Wii, perhaps not universal for any Wii game. Will have to look further into this, unless modeling can be done by code (C++, ASM, etc.) alone.

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Moved to ISO Modding Support, as this has become more of a discussion of ISO modding than a code request.

Mario Kart Wii has special tools for it made by Chadderz/MrBean, they cannot be used for other games. It's indeed kind of surprising how these guys did it but they're in a league of their own kind of.