Much like Korski tried to save Grass/Dragon with a final post in Typing, I'll try the same here for Cloud Nine.
I feel as though a lot of very unintelligent things are being said about Cloud Nine as an ability for CAP5. I'm not saying it has to be the ability. But here are the criticisms I have seen and my confusions/refutations:
I admitted fully in my first post about Cloud Nine making HP Fire an easy kill on any Scizor regardless of weather. One thing to remember is if Scizor's not under Rain that's a likely OHKO anyway. Second of all, we can fix that strength against Scizor by making Bullet Punch a 2HKO against CAP5 so that CAP5 still can't switch into Scizor, even on a neutral Bullet Punch. As a side note, being 2HKOed by a neutral CB Scizor Bullet Punch is not weak or uncommon. That's pretty par for the course in OU.
Could be used on other weathers, even as a switch-in against sun:
This is partly madness, partly fair. So the clear advantage of Cloud Nine is easing the switch-in for Sun teams against Water attacks, essentially starting us off taking 2/3 the damage we'd be taking if Rain were up. This is a significant amount. On the other hand, using a Cloud Nine Grass Pokemon makes no sense on a Rain team. It helps and hurts the wrong types. It doesn't even help against the key thing Cloud Nine could affect - Chlorophyll. We can make CAP5 lose to Venusaur regardless of the weather. It wouldn't even be that hard. Just be slower, so you get Sleep Powdered/Sludge Bombed. Now for a Sand team, a Cloud Nine CAP5 could find use, maybe. But I struggle to see just how it deserves a team slot. As a Rain counter, Sand has Gastrodon and Jellicent who perform quite well. Again, it wouldn't even help against Venusaur, and it's still weak to Fire, so it's not directly threatening Sun's sweepers in any way, even with the temporary weather removal. It really only helps Sun. It weakens Rain's spamming that so threatens Sun today and also helps against passive Sandstorm damage. I disagree with the statement that Cloud Nine is equally useful against all weathers. We're not talking about Cloud Nine in te abstract. We're talking about it in the context of a Grass type Pokemon aimed at helping Sun teams and hurting Waters. There, it clearly does its job.
Once Politoed is dead, it's pretty useless:
Um....... ok? I'll take it. Wouldn't a Sun team be willing to trade anything 1 for 1 with opposing Politoed? Seriously? That was a concern?
Increases accuracy of Hurricanes as compared to Sun:
Yes, from 50% to 70%. It also decreases them as compared to rain from 100% to 70%. And as has been discussed before, Hurricane is a much smaller threat now with Tornadus-T banned.
Cloud Nine neglects the concept:
The concept is to aid Sun. Not necessarily to make a Sun abuser i.e. Harvest, Chlorophyll etc. One way to aid Sun is to provide a good switch-in to, say, Specs Toed's Hydro Pumps. It has even been suggested that with Cloud Nine, CAP5 could run Hidden Power Water and threaten Sun teams. May I remind you that CAP5 can already "threaten" Sun teams with HP Rock. Don't talk about paper tigers as if they're real. If Sun teams lost to a Grass type carrying a super-effective Hidden Power, they'd be a bit beyond redemption. Clearly they're not that weak.
The Water spammage can be handled with good stats anyways:
I mean sure they can. But even Celebi, with it's 100/100 special bulk has to invest. Offensive Celebi sets are 2HKOed by Specs Toed. That's hardly a reliable long-term switch in. So unless we're advocating that CAP5 become a dedicated Special Wall with its EVs, it's going to have to have insane natural Special Bulk just to switch into the resisted attacks. And yes, Sun teams need a good switch-in to Specs Toed. Ninetales can't come in safe. It's a 2HKO there too, plus Ninetales hates hazards.
We decided we wanted to threaten Water types and Latis. We can threaten Latios with Pursuit after Latios has weakened itself to -2. Heck, we can give CAP5 Sucker Punch if we absolutely feel we must. But one thing cannot be changed by a move alone: Sun lacks good switchins to spammy Hydro Pump. If Rain is up, Venusaur takes at least half damage from just about anything's Hydro Pump. And Sun isn't even up, so Venusaur will likely be outsped and KOed the following turn. CAP5 can help there with one simple addition of Cloud Nine. That's the biggest impact I can see any ability making.
If you still see clear-cut reasons for why Cloud Nine is not good for the project, please provide a detailed response. I want to know why it's wrong. Because it sure seems right to me.