Amazing idea, however I would imagine it would be very difficult to create such a plugin. Also, I observe that when I use /texturepack with the Massivecraft texturepack, it makes my computer much slower and the lag unbearable. Your idea will most likely have a similar effect. Also, they would have to program it so that people in the faction who didn't want the texture pack didn't have to use it, which makes it all the more challenging.