I didn't want to build a (semi)stall team with the CeleTran core since ORAS is filled with stale ass fat teams as it is. So I decided to take a more unconventional route and went with CM BP Celebi and trapping Heatran. They still form a very good core together with Heatran trapping fat mons like Chansey and Cress, as well supporting Celebi setting up by outspeeding even max speed M-Scizor and Jolly Bisharp, and taking them out so Celebi's recipient doesn't have to deal with said fatness or get their item Knocked Off. I decided to go with Calm Mind Celebi over Nasty Plot since I figured you could just keep getting more and more boosts safely against Special attackers, plus CM Celebi beats SubCM Keldeo, CroBro, and Crocune pretty handily, while outspeeding Clefable and M-Sableye (no Snarl plz) so you can pass to Lando-I and Keldeo to beat them respectively. It also can fare well against TG Manaphy if they don't run Ice Beam (which none of them do). Celebi has enough speed to outspeed max speed Heatran and BP out before it can Taunt. The rest is then dumped into HP and physical Defense to check Azu and have great mixed bulk once you start to Calm Mind up.
Since I already spoke on the recipients a little, I'll fully state why I chose them specifically. Scarf Keldeo came to mind since it outspeeds every Scarfer in the tier barring the Latis (which rarely run Scarfs anymore since the M-Mence ban), has great dual STAB for cleaning up late game with at least neutral coverage, it can hit on both sides to beat AV users, and the only priority it's weak to is Talonflame's Brave Bird and M-Pinsir's Quick Attack. Next it went with Landorus-I since it already is amazing at cleaning up late game with Rock Polish as it is, so passing CMs to it is just a one-two punch. It can't be T-Waved, sits in a fairly good speed tier, is powerful as fuck as it is, has decent bulk, and is only weak to Aqua Jet and Ice Shard priority (the latter being very rare in the current metagame) and it has a wide variety of coverage moves on it that can cater to the rest of the team nicely. They both fare well against virtually every playstyle and can beat each others checks/counters very reliably.
I chose HP Electric so Keldeo can hit Slowbro and Tentacruel for good damage. I considered other coverage options like HP Bug, Ghost, or Flying, but Landorus beats a majority of the mons hit by those coverage moves as it is, but can't switch into Tentacruel and Slowbro, so it seemed the most beneficial. I opted to go with Timid Lando-I over Modest since i wanted to be able to outspeed Zard Y, which is pretty annoying for the team to deal with otherwise. HP Ice is for SpDef Gliscor and opposing Landorus forms, Sludge Wave is for decent neutral coverage and for hitting Unaware Clef, and Earth Power is just mandatory STAB.
My two CM recipients were both weak to the Latis, so I opted to use my mega slot for arguably the most well-rounded Mega in OU right now: Mega Metagross. It Pursuit traps Latis and opposing Celebi, beats practically every Fairy in the tier, and lures it fat Waters like Slowbro and Seismitoad, and removes them for Keldeo to be able to spam Scald late game freely (it's pretty funny when you Grass Knot a Slowbro on the switch-in when it's low, and then Pursuit trap it as it tries to switch). It also beats the only two viable Unaware users in the tier in Clefable and Quagsire, that way any CM boosts won't be in vain. I decided not to go for Hammer Arm since Heatran counters Ferrothorn and Skarm already, plus i have Keldeo and Hippowdon for Bisharp. Hippowdon was added as a Bisharp check so Keldeo doesn't lose its Scarf to a Knock Off, it also checks Talon, fast electrics like Megaman, Scarf Magnezone, Thund, and Raikou, checks Megagross that don't have Grass Knot, and M-Lopunny, Mega Beedrill, Sand Rush Exca, and it gets up rocks. Sand Stream > Sand Force is to help break potential Sashes even if Rocks don't go up, and to stop Rain and end Zard Y's Sun. Plus any chip damage is good when you're trying to sweep in one go, and can move damage rolls in your favor.