Moltres Day Duo/Trio possible???

Duo is possible with double rock ttars.

Smack Down/Stone Edge Tyranitars, friendship bonus and weather boost will definitely make it possible.

Moltres was duoable with Golem, easy duo with SD Ttars.

It was doable with Golem and even easier with Omastar. If anyone has a legacy Omastar, use it in first slot to get lots of damage off with Rock Slide and double resistance.

If Rhyperior gets a good double-rock moveset...

Defintely with Smack Down Stone Edge T Tars and Golems. I assume you can use Regirock, Solrock/Lunatone and Ancient Power Rayquaza if you wish but those are fillers at best.

Most certainly will be. It was duoable with Golems in the early days of raiding. Now that we have things like SD Tyranitar, weather boosts, friendship boosts, AND remember it will likely have T4 stats despite giving T5 rewards. I expect it to be a complete cakewalk.

Definitely.

I unintentionally Trio'd Zapdos on Zapdos day with two trainers who were below Level 30 and didn't have optimal counters (I had 4 SD/SE TTars and two Rock Golems which were Weather Boosted, the other trainers were using Aggrons!! and other Auto-Selected Pokémon), then intentionally trio'd it a few more times with other trainers. The first one we barely managed to get it done - like 5 seconds left. But the other times I did it when all of us had proper counters, there were 70+ seconds left on the timer each time.

Even if your Rock attackers aren't Weather Boosted, I would expect that a Trio of powerful Rock attackers will easily take down a Moltres Day Moltres. And if it's Weather Boosted? You should be able to duo it.