Just a little idea, while not perfect was to combine the 3 main maps from GTA 1 into one area.
I also upscaled each map by 2x of its original size.
I take no credit for the original exporting of this model, or the texture artwork itself. (I forget where I got it from, but it was exported quite some time ago now I also forgot who did export it) All I did was upscale the texture, applied it to the 3D model.
Liberty City Map - https://skfb.ly/oqZNo
San Andreas Map - https://skfb.ly/orUJ7
Vice City Map - https://skfb.ly/orUJv