6th Pokemon for Team?

The team seems to be more reliant on hazards then most other teams... so why not a spin blocker?

As you cannot trade, Gengar and Dusknoir are out of the question, but thats ok. Argueably the best spin blocker in 4th gen is the Rotom forms... assuming you can get another form then the basic form. If you can, I highly recommend getting one, putting a choice scarf on it, making it your revenge killer and spin blocker! As for the form, probably Rotom Cut, so you have a nice hit on Swampert, who, while most members can handle 1-v-1, you have no direct answer to.

However, the possibility of not having the event for Rotom forms is extremely likely, so there may be another ghost we can use. Rotom's basic form is too weak to use, and Mismagious is a poor man's gengar without Nasty Plot (And seeing as though you already have a Nasty Plot Houndoom, going that route probably wont be the best). Spiritomb would be a fine choice for the team, going a bulky rest-talk set, and spin blocking for your team as well. However, like Rotom Forms, the possibility of no Spiritomb may also be likely.

At this point, if the ghosts aren't avaliable to you, we should look for something other then a spin blocker, as Frosslass would be my last option for you, but even then, it doesnt fit the team all to well in my opinoin. If you want to give it a go, be my guest, but onwards to other options.

However, seeing as though you have access to hidden powers (which, btw, I would reccomend Grass or Electric on Houndoom; hits the waters harder. If you are stuck with dragon, it's better then Will-o-Wisp), I doubt you'll have trouble obtaining other pokemon.

If ghosts is unavaliable to you, the next best thing is get a solid revenge killer on your team, perferably physical, due to the primarly special nature of the team (Metagross is inconsistant as he is a lead, Skarm shouldnt attack too often)

When it comes to 4th gen revenge killers, my mind always goes to Weavile, but due to the cropping weakness to rock (stealth rock in particular) we have to find someone else.

Though speaking of stealth rock, get Rapid Spin on that Starmie! Houndoom and Dragonite would love it, and your other members wouldn't mind it either.

Heracross would make a pretty solid addition to this tea; choice scarf heracross. Able to outspeed every non-scarf foe he faces (except maybe Ninjask), and hit hard with powerful moves. While he has many checks, many of them hate stealth rock, and will slowly be worn throughout the match (and skarmory checks some of them too)

If you want to stick with your ground-type idea, Choice Band Mamoswine is an excellent wall breaker and revenge killer; just make sure to breed to get Ice Shard on him!

Hope I helped!

OH MY SNIVY!

That's an incredible team... -Starmie.

I have only a few comments.

I think Metagross should know Ice Punch to counter Ground types.

Skarmory probably should know a steel type move, like Iron Head or Steel Wing.

I personally think you should replace Starmie with Milotic, since Milotic can learn Psychic.

But that's just me.

Ice Beam

Surf

Psychic

Dragon Pulse

I'd EV train that in SpAttack, Speed and Sp Defense. (252, 252, and 4)

EDIT: I just saw you couldn't trade- no Rhyperior. ;_;

In that case, use a Garchomp and EV train it in Speed so no ice type can outspeed it.

Grachomp

Stone Edge

Earthquake

Dragon Rush

Crunch

252 Attack EVs, 252 Speed EVS and 4 in defense.

I think that is one solid team you have. I'd be afraid to face you.