This assumes that:Ugh I think the Fairy-type would be totally fine, but dual-typed moves? >:( It just seems as if it would massacre any sort of defensive Pokemon. A Ferrothorn or Jellicent? Don't worry, I have 8 different attacking types to hit it with... Other than that, I really love all the new additions. gogoat!!!
-Dual type moves work by literally attacking with two types at once
--And assuming the types deal SE damage that can stack
--And assuming the dual typed moves have useful dual typing (finally, the normal/steel move everyone's been waiting for!)
-That they will be widepsread
-That most pokemon that want them will get them
-That they will be strong/useful/worth using by most pokemon that can use them
-Don't have like a dozen caveats