People who complain about Bungie being lazy or what have you probably don't have a clue how programming works. Could they have made entirely new character models? Sure, at the cost of hundreds of man-hours to make, rig, animate, skin, and test them. If you've already got a working model it's a helluva lot easier to reskin and give new abilities. Plus it's not like people complained the red koopas were reskinned green koopas