The way Nexon looks at the whole issue if someone can texture mod an item then they are also capable of changing the textures on how others appear to them. Thus it is consider a hack.
When Nexon does its compile in the future and repacks the game, they could very easily seperate individual models and other models, this would make it harder for hacks or mods to be used as an advantage to any players. (In other words, your texture models would only effect your view of yourself and no other character in game) But currently this game is very simple when it comes to models and textures and that is why hacks and mods are so easy for some to be made, cause the majority of these files are client side, or temp files when the game is running. If they added in a 30 second or even 2 min check against server side, they would stop most mods and hacks from working very simply.