Sidekick is more for a familiar in the wizardly sense. You could always add unique attached miracles or flaws that further customize what it is you want the power to do. It also depends on what you feel the power should do and how appropriate that is for your game.
Useful (summon/create scorpion), if/then 1 at a time, endless 2hd
Useful (enslave scorpion) attached, endless, if/then 1 at a time 2hd
Useful (Increase Scorpion size) attached, endless, if/then 1 at a time 6hd
Defends (scorpion armor), attached, endless, Armored Defense 3hd
Useful (extra tough on scorpion) attached, endless, if/then 1 at a time 5hd
Attacks (giant scorpion sting) if/then giant scorpion active, burning whatever dice
Attacks, Useful, Defends (giant scorpion claws) if/then giant scorpion active (just buy a couple hyper body dice with range capacity) 5d