Jim, it would be completely sufficient to map GJ to V2. As DPH points out above, the "Universal" (hollow laugh) Texture Converter will convert V3 textures to V2, so if you had GJ taking V2 textures, she could also use any V3 texture, assuming the user has UTC.

It would improve the usability of the product so much, it might very well be commercially worth your while to persevere.