RIP

The best i can tell you is that in GTA 4 they had this function on some cars GPS units. if you could find out how that works maybe it could work in GTA 5

I dont think its possible. They both run on completly diffrent engines

Well isn't this for all mods in general?
Dont get offended but this will happen regardless, you are expecting hundreds of people on the internet to follow your rules and theoretically someone will disobey the rules just to spite you. And anyways, why would you restrict your mods? that just makes reposting mandatory. Lastly, no The japanese did not withdrew their characters. you can still download various Touhou character moddels of their blog pages with a bit of japanese or google translate. This wiki litteraly has a huge page of touhou characters and from diffrent developers. modding is all about sharing your creative piece. It's the same with artists online, did you pay or watermark your anime wallpaper, or did the artist give any credit to the development house for the character they drew on their pirated Adobe Illustrator? No they don't.