Well, the team starter was not Metagross, but instead Sunny Day Heatran. I had thought about using Sunny Day Heatran when I wanted to use Heatran, but I was annoyed that I would be forced to use Life Orb+Hidden Power Grass just to hit Water-types. I had actually gone and done a whole bunch of calcs to see how Heatran would fare against Water-type attacks in the sun, and how much Solarbeam would deal back in return. The calcs seemed extremely promising, so Heatran got on the team right away.
Next, I considered what Heatran was cockblocked by, and the simple pattern was Special walls and Dragon-types, especially Dragonite. I figured I would deal with Dragons later on in team building and focused on the special walls. This allowed me to also use a Pokemon that I actually used before and loved to use: Choice Band Metagross. It had everything I could have wished for: priority, great bulk and typing, and insane power with Meteor Mash.
With my two-punch offensive core made, I realized it was destroyed by pretty much any strong Earthquake user, so I had a plethora of Pokes that could have worked. The fact that I was using Sunny Day really ruled out Rotom-W, and I also wanted this Earthquake immunity to have some good bulk so it could survive a few mispredicts and use its resistances, so Gengar was trashed. that left really three options; Dragonite, Salamence, and Hydreigon. Hydreigon was chosen because it had good bulk combined with great Special Attack and was not weak to Stealth Rock.
After my three-part core was finished, I was not sure as to where to proceed. I Had U-turn on Hydreigon, so I thought that adding another U-turn user could only help. I didn't want to use Scizor because i already had Bullet Punch on Metagross, and I already knew my team was Volcorona weak enough. Thus, Mienshao earned the fourth spot on my team. Hydreigon could easily mutilate Mienshao's counters, and Mienshao could run through Hydreigons.
The next thing I added was Breloom. There wasnt any real good reason I remember besides being able to royally fuck over Voltturn cores and to provide Sleep.
Lastly, I needed a Stealth Rock user in order to actually make this team threatening. At the same time, I realized how much Dragons could just tear my team a new one because of its general slowness. I managed to slove both problems with one Pokemon: Mamoswine. It could easily revenge kill Dragons with Ice Shard, and setup Stealth Rock as well. It also had plenty of offensive presence, which was never a downside.
After building the team, I took it for a test drive and almost immediately I found the one fatal flaw; It was just too damn slow. Fast sweepers who weren't weak to Ice Shard or Bullet Punch could just rip right through the team with no effort, and Fighting-types could just spam their STAB without any fear. Fustrated, I knew there wasn't one single solution to both problems so I focused on my Speed issue. I needed a Scarfer, but I couldn't find one that I thought would work. Eventually, I went with Haxorus, and it preformed marvelously. Haxorus took the place of Breloom because Breloom was the obvious weak link from my testing, and I could already handle Voltturn cores with relative ease.