Thanks for the script. But, adding the option to MTA would be the best choice IMO, because we are telling the server not to download the mods. If we depend on the server via script, then regardless whether we want the mod applied or not it's going to download the mod anyway, which wastes bandwidth(if we don't want the mod). Unless, the server script lets the player decide whether he wants the mod to be downloaded or not(via simple popup message), then it's fine.
If MTA has the option, it should only be applicable to servers that replace the model and textures of the vehicle only(DD/DM). If the server has handling and other data assicoated with the mod, then MTA should allow downloading the complete mod and replace it by confirming via a popup message.