I just decided to throw this out there but I just realized that Mega Rayquaza's Ability Delta Stream nutrilizes all flying type weaknesses. Now Tournadus Therian form is a mono flying type so does that mean that while Mega Rayquaza is out Tournadus Therian or Arceaus with a Flying Plate have no weaknesses? If so do you guys and gals think that this combo is any good or no.
I think that just because a Pokemon has no weaknesses doesn't mean it's the best (see Eelektross). Although I like the idea, there aren't many formats in which you will be able to use it. Probably the only place you would be able to play with it is in an unrestricted doubles or triple battle on Showdown.
I pretty much have to agree with @Joushou Pokemon having no weakness really doesn't make them good. Although considering these Pokemon's stats it actually would be kind of cool but then again I'm sure they wouldn't be allowed. We'll just have to wait and see.