This would be a nice idea, but to be honest I feel it should be more expensive than the joint texture item itself. Here is my reasoning:
Joint textures give you artwork on that specific joint, but they do not change the underlying hue that the force/lax already gives. This results in "off" color results, because if you have copper force and a joint texture set to white, it will still show as orange, no matter how lightly drawn.
People spend lots of money, and time, to earn the Pure color for this very reason, so their colors are no longer muddled out by another. This single joint force/lax would result in further customization options, but to assume that this individualization would come at cheaper would devalue both the cost of pure, and the time/money spent by the players to earn their colors being exactly what they want.