Is it a Shield then? If so, I think you should find space to fit the word shield on the card. Removing the skill nae should do. ALso, since the upped and unupped decoy are different, I think the name should be different too (or simply don't name it?)
Anyway, decoy can be lobotomized, but does it replace the target's active ability? That would seem OP, as it would essentially make this an insta-kill.
Could you elaborate on the unupped decoy? The creature does its full Atk to a friendly creature chosen at random?