@DrDuckling This is Mashima Hiro we're talking about.
He probably planned for all these plot twists, but his hack writing ability doesn't allow him to see the shortcomings of this method (and how much retconning he ends up doing along the way).
In other words, I think he planned it, but he's bad at it!
Seriously, Drakken didn't know they were going to invade his ship nor that they would try to rescue the B-cuber girl.
WHY WOULD HE HAVE HIS SHAPE SHIFTER MINION PRETEND TO BE THE GIRL HE KIDNAPPED IF HE DIDN'T KNOW THEY WOULD COME FOR HER!?