Gen 6 doesn't introduce a new type, but merely modifies the existing type chart to fix the meta. What would you change /vp/? Assume other changes such as weather nerf still happen, but mega evolutions do not.

Personally I would do the following:
>Steel still has Dark and Ghost resists removed, but is now super-effective against Dragons
>Ice gets Dragon and Flying resists, but is in turn resisted by Poison
>Poison is super-effective on Fighting
>Grass gets Fighting resistance
>Dark is no longer immune to Psychic, only resists it
>Ghost no longer resists Bug