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Bug/Psychic Both types are really cool, so I wouldn't be disappointed with either result. I do think that a secondary Psychic typing fits better, however, there are very few risks, type wise, that Dragons have.
Maybe Bug/Psy has a harder time to switch in/out battle, thus a higher inherent risk, but unless CAP 4 has an insane amout of power or a pretty specific niche i feel the reward couldn't be the best. Maybe I'm wrong, he he.
I feel that Bug/Psychic is the more likely option to produce a good, risky CAP. Bug/Dragon, to me, seems all to easy for us to get wrong and either make it too easy to use or too weak/outclassed.