This device could be 1.5 fingers wider, the increased size placed to the right of the wheel.

i am a pianist, and have made a mold to create this change. The current shape of the mouse creates issues in the 4th finger (of the right hand, right-handed mouse) that causes issues with the Flexor digitorum Profundus muscle, and creates temporary rigidity in the medial portion. I think that at least an extension could be made, similar to what I envisioned, that allows a more healthful use of the hand.