You accidentally made me realize something. The keypad would probably be better on the left than right. There’s nothing to the left of most people’s keyboards, and presumably you have your keyboard positioned in the best place for your hands regardless of keyboard layout. Shift the keypad, and other buttons, to the left instead of right would make more room for the mouse.
Edit: This is apparently already a thing, labeled as “left handed” for some reason. I’m not sure what being left/right handed has to do with it though because we all type with both hands already.