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Plus, being Dragon/Poison would mean Steel types get an advantage, meaning that the Sketch move would be set aside for Fire/Ground/Fighting, which would really ruin the intended versatility.
Sticking with this Combo, I like it for a number of reasons, it's resistances are very cool and it has a neat attacking type. I'm looking forward to this project.
Dragon typing makes choosing a coverage move too predictable. The poison off-type is nice but I think that Grass/Ghost is all around better for experimenting and would make for a more interesting CAP.