What should CAP5 be able to threaten:
- Lati@s: The main attractiveness of the Dark type is to be able to hit those two Dragons, that are a big threat for Sun teams. How to implement this can vary quite a bit, in my head this means very decent special bulk to be able to take an attack or two, however this may be poll jumping or just another road could be chosen. The important thing is to be able to switch in somewhat and threaten them immediately.
- Water types: Our Grass typing covers this mainly, since it allows us to take a couple hits and threaten back with powerful moves by both sides, depending on the stats we will choose. We do not necessarily want to be able to force out any Water pokemon, just to make them think twice / three times before risking the switch into a Grass move. However if Keldeo finds a way to come in, it's ok for CAP5 to be threatened by its Fighting STAB.
What should threaten CAP5:
- Steel types: As someone already said, Steel types are a good switch-in opportunity for Ninetales, and Sun teams are generally fine in dealing with them. I do not see a big concern the fact that they can switch into our STABs with a good degree of freedom. The one I'm not really sure about is Heatran, since Tales doesn't really want to switch into it, and Sun teams have a generally hard time against it. If Rocks are down on our side, Dugtrio is a risky play, since Heatran will try to roast our Grass pokemon anyway. To this regard, giving it U-Turn and no ways to hit Steels effectively looks a good idea to me, being able to switch into Duggy / Tales without too much fear, while allowing us to focus on our main target (Dragons).
- Fighting types: Our Dark typing is crippling here, but I think it's generally fine. Breloom should be able to check CAP5 to a degree, switching into any STAB move somewhat (it probably should try to avoid a Sun boosted HP Fire) and threaten out with Mach Punch. This is not a problem, Sun teams often carry Cresselia, Xatu or something else that can deal with Breloom easier. Other Fighting types will be able to force us out after being switched in, but many of them will have to gamble on the switch-in (Keldeo, Terrakion can't stand being hit by a STAB Grass move).
These are the main, most obvious things that we should pay attention to, in my opinion, although here are a little bit of other things that may be worth discussing (for example, we may want to threaten Psychic types to an extent, we don't want to give Deo-D or Celebi free switches, however this is implicit in the typing to an extent).
So yeah, this was a big post to say I agree with Pwnemon almost 100%...
Let me do another little comment before closing this: while Rhys DeAnno's post does make sense, it is just a massive poll jump since you assume that the main role of our pokemon is to spin. Giving a Grass / Dark pokemon the ability to spin means making it able to defeat all the main spinblockers while being very likely to have access to Pursuit...which is indeed a incredibly nice way to remove hazards, so nice that all thos DNites / Mences / Kyu-Bs / Thunduruses / whatever will thank us a million times and proceed to nuke Sun teams with their newfound bulk.
- the main focus should be to threaten Dragons;
- we should be able to hit Water types hard, at least on the switch;
- U-Turn should be considered to give us a nice way to safely switch to our checks for Steels / Fightings / whatever;
- Steel types should be able to force us out by resisting our attacks (perhaps even coverage ones);
- Fighting types should have a hard time switching in (except Breloom thanks to its typing) and and force us out once there.