It looks to me like the biggest threat to this team is opposing Spikestackers. The Snorlax/Swampert/Cofagrius defensive core is relying on three grounded Pokemon with no reliable recovery to take hits; the team's revenge killer, Darmanitan, is also very vulnerable to hazards. As there is no spinner, once hazards are up they'll stay up, which makes the team pretty easy to wear down if it can be forced into repeated switching. In particular I see a weakness to the rare LO Galvantula - its Thunder is strong enough to 2HKO Snorlax 40% of the time after SR and one layer and OHKO Zapdos after rocks. Swampert is also OHKOd by Giga Drain after SR damage and Cofagrius takes a very large amount, so even if it is able to stop Galvantula it will be too crippled to take on something like Heracross later in the match. Of course, Darmanitan can easily revenge, as can Frolass if it is still alive and Galvantula is weakened, but both Pokemon are grounded and SR weak, and Froslass is a suicide lead, so they are very prone to being worn down/simply KOd in Froslass' case. I imagine in general the team is a little weak to any Pokemon capbable of dealing with the defensive core. Things like SD Virizion, Rain Dance Kingdra, Nasty Plot Mew with Giga Drain and perhaps even a well played DD Scrafty if key pieces are weakened. Mostly, special attackers that can beat Snorlax and Fighting-types that can beat Cofagrigus. CB Flygon may also be an issue, as it comfotably 2HKOs every Pokemon on the team is is tougher for Darmanitan to revenge kill - Zapdos can't always beat it either, as it does not carry HP Ice. Flygon is easily revenge killed by Froslass if it is still alive, but as it is a suicide lead, that may not always be the case. That said, the team is very solid, and all of these Pokemon can be revenge killed or played around without too much difficulty.
I expect that the goal of the team is to use Darmanitan's U-turn along with the threatening presence of Zapdos to repeatedly force bulky waters to take damage from hazards, until a sweep can be achieved with scarf Flare Blitz. Even Slowbro, who does not mind hazards, is quickly weakened by repeated super-effective U-turns. With HP Grass, Zapdos is able to KO Swampert and Rhyperior, two common Darmanitan checks that it would otherwise struggle against. Gligar is less of a problem because it does not need to be weakened as heavily for a Darmanitan sweep to be achieved; additionally, it can only really damage Zapdos with Toxic. Chandelure, another possible Fire-type switchin, is trapped by Snorlax and KO'd with Pursuit. Additionally, Swampert can take it on without too much trouble if Chandelure does not carry Energy Ball. Defensive Arcanine and other similar bulky Fire-types can be beaten without too much trouble between Snorlax and Swampert.
The defensive core of Swampert/Snorlax/Cofagrigus is the backbone of the team. Snorlax walls most special threats in UU, and Swampert can also check many of them, which helps to ease the load on the recovery-less Snorlax. Cogagrigus round out the trio by taking on the Fighting-types that threaten Snorlax and generally being very bulky on the Physical side. Additionally, the possibility of a Nasty Room sweep gives the team an extra win condition. Both Snorlax and Cofagrigus are offensively EV'd, which ensures the team is never left in a position where it does not put pressure on the opponent. This is very important to minimise the the opportunities hazard layers are given. As mentioned, the offensive core consists of Darmanitan and Zapdos. Darmanitan's revenge killing ability and Zapdos' bulk and resistances also offer the team an improved ability to handle threats, something very useful in an offensive core. Froslass' job is mostly just to die while setting up as many layers as possible; however, it is also able to use its combination of speed, Taunt and Destiny Bond to harass the enemy team if it has finished laying Spikes or if it is more useful in a harassment role. The use of a more defensive EV spread makes Froslass less vulnerable to multi-hit moves, which is handy when condsidering they would otherwise break through her Focus Sash. Cofagrigus amnd Swampert should handle common multi-hit-move-users fine between them, although Cinccino could be annoying as it is able to OHKO Swampert with Bullet Seed and is not OHKOd itself by Cofagrigus' unboosted HP Fighting. It is unlikely to be able to 2HKO Cogagrigus without some luck, but it will often 3HKO, which leaves a big dent in Cofagrigus and prevents it from achieving much the rest of the game. Having said that, Cinccino is a very rare Pokemon and RT. can easily chose not to lead with Froslass if he sees it in team preview.
I believe the consistency of the team lies in the small list of solid counters to Darmanitan combined with its access to U-turn and the perfect offensive partner in Zapdos. Froslass' ability to almost always force multiple layers is also crucial, because it means the opposing team will be playing with multiple layers up no matter what they try. This greatly amplifies the effectiveness of Darmanitan's U-turn, allowing a sweep to be achieved more effectively. Additionally, the populatiry of sets such as Choice Band Snorlax that are reasonably easy to wear down makes Zapdos very threatening in the current metagame, because it demolishes most of its counters after a couple of hazard switchins. Zapdos is also pretty fast for UU; this improves its ability to force switches, causing yet more damage from hazards. Snorlax's Choice Banded Pursuit is also a small factor, because the ability to easily remove Chandelure, a threatening Pokemon which also happens to wall Darmanitan, is very handy on any team. Chandelures unique palette of resistances make it a pretty annoying Pokemon to deal with, but this team traps and KOs it without much trouble. Beyond that, merely the fact that pretty much every team member contributes to the goal in some way is a big advantage for the team, as it make the whole team easier to play and means the team will naturally achieve a sweep if played intuitively - this simplifies laddering and makes the team as a whole more resillient against luck, because no team member is absolutely crucial to the overall plan.
It difficult to suggest changes for a team this good. Making Cofagrigus more defensive would somewhat help the Flygon issue, but it's still a poor answer with hazards up and Cofagrigus becomes setup bait for spikers with this change, exasperating the existing issue. Similarly, making Zapdos much more specially defensive may help deal with special attackers, but it compromises the overall team goal but limiting Zapdos' ability to remove bulky waters. In terms of more sweeping changes, replacing Darmanitan with a Pokemon less vulnerable to hazards would probably improve the teams ability to deal with various threats, but I can't think of anything that has the raw power of Darmanitan and the ability to lure bulky waters. It may be worth trying a scarfed Mienshao in this slot as it can still U-turn out of ghosts to have Snorlax trap and KO them, but I don't believe it would maintain the same level of team synergy. Overall, the few weaknesses present in the defensive core can generally be dealt with via revenge killing, and the hazard vulnerability can be mitgated through intelligently agressive play.
EDIT: Forgot to mention, this is a really fantastic thread idea.