fenyxofshadows makes a good point, it was the introduction of Thundurus-I and Klefki that brought this annoying strategy to prominence, full OU teams whose whole strategy revolved around it only sprang up later. If we were to ban those 2, I'm more than willing to bet that swagplay teams would decrease and single abusers would almost cease to be a problem, but I don't think swagplay would go away entirely. We'd probably still have to deal with the occasional troll trying to ladder without bothering to come up with any actual strategies or teams besides "swagger, then Twave, then foul play until my opponent rage quits!"
I'm not quite sure I agree with Klefki being broken like MGengar was, but getting into an argument about that wouldn't be productive, so I'll leave well enough alone.