Thank You for interesting info! IRL I kind of have a "license plate fetish", so, after a few months, I am still "learning" the "carcols" part, especially how to properly set up these "extents". Although, I haven´t tried adding plates (I guess 5 is enough for me :P). In theory, if the license plates textures are in vehshare(and named properly) and if they are "registered" properly in carcols, then I don´t foresee problems, because (in theory) You are doing everything, what is needed. For example, adding new vehicles is not that different, You also need to add model/texture files(as the textures in vehshare for plates) and "coding"(by that I mean vehicles,handling,carcols,carvariations). There could be a line in an unknown encrypted file(not all the files are accessible to date) called "MaxLicensePlateNumber" or smth like that, but as far as I am aware, no information about such thing...
I will soon release my mod with 5 modified plates + proper carcols lines.
My question is, what does Menyoo say? Does it also name these 2 new plates as "Street" and "Sport" or is it only in enhanced trainer? Where does that trainer take its info from?