I looked back through the other thread, and there was very little reasoning for Dragon aside from resitances and the coolness factor. Some went off on how a defensive dragon was "needed". Tay had probably the best argument from all that I skimmed, and even then I don't see why it should be chosen OVER Dark or Ground. Even No Secondary seems like a better choice.
I dunno. I really dislike how people are just jumping for it immediatly when they see the word Dragon. Sure, a poisonous dragon sounds pretty cool, but that's hardly why we should choose that typing.
I'm still curious what design we'd go off of if we did do Poison/Dragon. It can't be serpent-like if it's going to be based on utility, I think. A turtle Dragon is the best thing I can think of for a defensive dragon, but that doesn't include poison (unless it's a breath attack ;/). We can work on a dragon next CAP project, just, we need a good utility pokemon, and I think Dark and Ground do that better.
:s
Dragon does make it easier to justify Psychic-like moves on a Poison-type, it's been explained before. The moves Ground, Dark, Electric etc have aren't specific to their type either.
As does Dark, but then again, it depends on how we stylize this pokemon. I don't see a serpent, which many in the last thread seem to think this would be, setting up mental barriers and pulling down flyers with it's mind.
Flavor wise, Electric offers the screens readily, TWave, maybe magnet Rise... Something like electrode.
Ground gives SR and spikes, sandstorm, gravity fits in, etc.
and Dark has a lot
http://www.serebii.net/attackdex-dp/dark.shtml
While they aren't completely specific, they fit into the pokemon's designs more readily, I think.