Well, when I think of "Stall breaker and defensive mon" my first light is Gliscor; but since it's banned, we do have Gligar. Eviolite and Roost give it acceptable bulk, and in terms of tools it has nearly everything in Gliscor's vast array of options like Taunt, Knock Off, and Swords Dance. Immunity stops Toxic stallers, and weaknesses are easily covered by Feraligatr, Suicune, Azumarill, or any other Water type.
And no, 6IV ditto would never get you banned. They have absolutely no way of reading or obtaining data on HOW your pokemon was bred and shit; disconnects however they monitor with reasonable accuracy and objectively prove you disconnected. Which, they can forfeit your ranking for.