Unless I have missed it, I think that there should be a more gradient options, up to three or four, that you can have going in any of the pre-existing directions.
I also think that there should be just a colour-change option so that you can split the keyboard in 1/2, 1/3, 1/4 etc, and choose different coloured notes and sabre for each section, i.e split the keyboard into two and have red on the left side and right on the blue side, with no gradient.
Edit: I also think we should be able to add any colour lights that look like LED strips :)
Edit 2: Also, I think you should be able to change colours and gradients throughout the piece, i.e start with a red + white gradient and then swap to a different solid or gradient somewhere in the piece