I suspect the end worth of being able to dye every pixel would in the end be a bit less exciting than it sounds.
What I would like to see... and something I have a particular mindset for implementation along a similar standard already used for UO... is the ability to dye a single item with multiple hues. Knowing how UO handles its current hue system, and also knowing that much of what should be able to be hued isn't properly because later DevTeams either forgot or ignored that they shouldn't be creating cloth in full color, I'm certain a system could be implemented where you could dye different portions of an item with different colors. Now, mind you, it would require some retooling of existing artwork to make it work, but the system would also work in a 3D/textured environment too as long as the standards were adhered to.
Thus, say you had a candle... under the system I'd see implemented, you could manufacture the base of it in an appropriate metallic color (either through ingots or the metal dyetub -- though... ugh... what a goofy dye tub), and then you could dye the candle itself another color (perhaps a combination of the plant pigments and beeswax to do so... thus adding a use for beeswax AND another use for plant pigments).
So many systems, so much improvement could be made.
But in short, I'd rather see multi-hue objects implemented at some point rather than "dye every pixel." Allowing someone to change every pixel, in essence, would allow things to fall outside the flavor of the game, which would be a bad idea if you ask me.