Going to start on some dialogue already. I love Bug-type for this concept and I think DarkSlay hit the nail on the head with his proposal. It has a good amount of weaknesses, resistances, and STAB options. It also has some great status-upping moves, which inherently have a lot of risk incorporated into their use in competitive play.
I made my original post in this thread because I first wanted to warm you guys up to the idea of Dragon at least playing a role in CAP4. However, my ideal typing would be Bug/Dragon
for CAP4. In order to understand the rest of this post, please read DarkSlay's comments above mine; he echoes a lot of my thoughts that are built upon with my argument. Let me run down why exactly I think Dragon-type is the best complementary ability for Bug-type.
At its current state, Bug-type doesn't hold too many resistances. Let's add more. This is something that I've chatted about avidly in #cap on multiple occasions. I think that the risk factor associated with CAP4 should be about what it does when it is in play, rather than the risk of switching it in. Let me clarify. I don't want to make a Pokemon that constantly has to worry about switching in due to its startling weaknesses. I want it, rather, to have some solid switch-ins so that it can begin to set up and take some risks. Adding Dragon-type gives some great resistances. Ever-present Water-type STAB moves in the rain are killer in this metagame; having a way to resist that (and Electric-types moves to boot) is really essential in giving CAP4 at least a fighting chance in the rain.
Dragon-type doesn't mess with many of Bug-types weaknesses (only Fire-type attacks). We'd still leave CAP4 vulnerable to Flying-type and Rock-type moves, which is advantageous in the case of CAP4. Having that Stealth Rock weakness in tact is key to making sure that when you use CAP4, you are taking a risk; it cannot be used many times before it dies from accumulating damage.
Bug and Dragon STABs is good offensively, but not spammable. Both types are still resisted by Steel-types, so it doesn't have any excellent way of getting around them (not without setting up, at least). As I listed above, there are also inherit risks to many Dragon-type moves, so that is something to consider.
It remains neutral to many kinds of priority. I think that this is key to note, since there is risk involved with keeping CAP4 in against a Pokemon that might finish it off with priority. It resists Fighting and Water, but it also has a weakness to Ice-type priority. That, combined with neutrality to Ghost, Dark, and Normal, leaves CAP4 at a pretty happy medium in terms of priority.
Basically, I love Bug/Dragon because it fills in the two points that DarkSlay made that are currently not in the green "checked" position. First, it adds some more resistances for it to play with, but not an obnoxious amount. Also, it adds in some STAB moves that do indeed have some inherent risk (Outrage and Draco Meteor). Hopefully this post has helped clarify why Bug/Dragon is a great set up for a high risk and high reward CAP.