Woo first set post in this type of thread, and it is weird but I'll go for it anyway.
BirdyTrans!
Heatran (M) @ Air Balloon
Trait: Flash Fire
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Fire Blast
- Toxic
- Earth Power
- Dragon Pulse
Explanations: Timid over Modest because we can now outspeed both Excadrill and Mamoswine. Fire Blast for general hell raising, Toxic is a big deal to cripple Ho-oH and Lugia, and Dragon Pulse so opposing Dragons don't use us as set up bait. Earth Power in case they throw in opposing Tran.
Well Shit, TSR
They have 3 ground types with Earthquake.
Yes but we have Air Balloon, moves that can 2HKO (or OHKO) all three, and outspeed them all.
Hippowdon:
Fire Blast: 57.47 - 68.03%
Excadrill:
Fire Blast: 154.14 - 181.21%
Earth Power: 77.34 - 91.16% (More reliable accuracy in Rain if scenario arises)
Lugia:
Fire Blast: 30.52 - 36.29% not so pretty but Toxic will hurt it severely
Mamoswine:
With a change to Thick Fat, Mamo stomachs a Fire Blast for a hearty 81.99 - 96.95%
Speculation and Looking Ahead: Currently Team Two is mega weak to Kyogre's water STAB, with their only salvation being in a) changing weather back to sand and b)adding adding major water resists to make up for this fact. Looking ahead, two of the best counters to water are Ferrothorn and Palkia, one being defensive and the other being offensive.
Ferrothorn takes 75% from Fire Blast in Rain, easy OHKO in neutral or sun.
Palkia takes 52.95 - 62.3% from Dragon Pulse but we wouldn't want to stay in on it anyway for fear of Hydro Pump, but I'm just being thorough.
I just wanted to try and think ahead in their teambuilding process.
I will say that this opens us up slightly to CM Fight Arceus, we just gotta stay on our game and it won't be too big of a threat.
Also I assume that Team Two can go back and change their Mamo to Thick Fat, the OP says they still have Oblivious.