I want all my necessary shortcuts under my left hand.
Im used to moving around in some editors with WASD and it kills me that prezi doesnt have this feature but also it is my hands default resting position.
I construct network diagrams mostly and theres alot of copy pasting happening aswell as moving around objects. I want to have the least amount of movement in my hands because copy pasting is uncomfortable on my keyboard.
Automatically cloning an object by middle clicking could be a nice shortcut for me too.
Also since prezi can be used for so many different things, shortcuts should be customizable to suit your needs :)
Click drag selecting multiple objects will prove useful too, but again not everyone needs this so customizations: yes :D