A suggestion, if possible, is to add an option to VrayDecal to apply it to a specific material. For example, in the case of objects with multi-material, apply it only to the specified ID or material name.
Is there a possibility to use Corona maps for GPU? There are some maps very useful that Vray doesnt have (Corona Tiles, Corona Front/Back, Corona Map Select, Corona Color Correct)
Other renderers can convert textures to a tiled and mipmapped texture format before rendering automatically. The maps referenced in materials would still be pointing to the original png or jpg but the renderer will auto convert those to .tx or .ra...
Corona has this map that its very useful for Vegetation, right now is compatible with Vray, but not with Vantage, the procedure is to create a Vray2Sided with 2 materials as usual