Well, I don't know about MnM Doubles but I know Dragonite is actually laughable in regular Doubles so that might be worthy of a check. Cresselia I would honestly give it a hard no to unban. It's one of the better Pokemon in regular Doubles and I can see it being downright terrifying in MnM Doubles. Lucario might be worth a check because it's all around frail.
Dragonite is actually quite effective with Weakness Policy in Doubles, in no small part because hazards are less common. It's not at all unusual for it to get a Dragon Dance, get the Weakness Policy trigger, and murder at least one thing. Spreading status is also less common in Doubles -it's usually easier to just straight-up kill things than to go through the effort of crippling things. So Lum Berry Dragonite isn't as necessary, and the lack of such on MnM Dragonite isn't going to be missed as much.
Of course, this is MnM, but the ability to Dragon Dance while Multiscale ensures its survival and
then Mega Evolve and Extreme Speed something is my point.
Regigigas might be worth a test. It doesn't get protect, and I'm not sure how slow start works with mega-evolving.
Cresselia is just nightmarish either way. The fact that it DOES take a +6 rock slide is pretty troubling, meaning you have to attack it with both 'mons.
Also, Cress isn't necessarily going to take the +6 hit in the first place. Many Cress run Trick Room, and with Sablenite/Audinite Cresselia's bulk, it can easily run, and support, a trick room team.
Slow Start clears away when the Ability is cleared. Unless MnM's code is
really weird, Regigigas will be good to go first turn, only having to suffer through halved Speed for one turn.
If Cresselia is spending all its time healing itself and
still losing more than 50% of its health,
while its buddies are dying, it's an active liability.
252+ SpA Hydreigon Dark Pulse vs. 252 HP / 4 SpD Cresselia: 204-242 (45.9 - 54.5%) -- 57.4% chance to 2HKO
Altarianite Hydreigon hitting Sablenite Cresselia. Unlike Standard, we don't need to assume Cresselia came in on something that can't do jack to it and got up a Calm Mind. That's just not how Doubles works.
252+ SpA Pixilate Hydreigon Hyper Voice vs. 252 HP / 4 SpD Cresselia: 150-177 (33.7 - 39.8%) -- guaranteed 3HKO
Or it can dish out damage to Cresselia's ally while pressuring Cresselia, forcing it to keep healing itself as an incidental effect, rather than a dedicated attack.
The thing that makes Cresselia ban-worthy in MnM Singles is that it can set up and sweep while ignoring everything short of
extremely powerful Physical Dark, Bug, or Ghost attackers that are also running setup, with basically only Dragon Tail, Circle Throw, and Mold Breaker providing any chance for a more stall-y team to do anything to it in, too. In Doubles, it's not going to be able to setup against offense, because it will be too busy healing itself, assuming it even survives, while stall is both less common in Doubles and
different in Doubles. (I don't personally have a lot of experience playing Doubles stall, so I can't provide clear specifics, but it behaves rather differently than Singles stall)
The improved ability to run Trick Room is definitely worth commentary, especially since barring Mold Breaker you can't Taunt Sablenite Cresselia, demanding Fake Out to prevent first-turn Trick Room, but being an amazing Trick Room supporter =/= being broken.
I don't think it's THAT laughable in regular OU. It might not be the best but you can't actually make it work.
Besides, Extreme Speed isn't really as useful in Doubles as it is in Singles. In terms of -ate spam, I'm more concerned with/interested in -ate Hyper Voice from all the ridiculous special attackers now. Hyper Voice hits both opponents so you just put on a good stone on a Pokemon with a high special attack and be done with it. Something like Altarianite Hydreigon might prove interesting just to try out. It'll make yourself a nice Dark/Fairy type and give you a pretty good 165 base special attack. No speed increase but it won't need too much really.
Speed tiers are weird in Doubles, because you don't have the same room to maneuver for Dragon Dances but it's also much more realistic to get Tailwind support.
Priority is actually
more useful in Doubles than in Singles, for letting you pick off a key target before anything moves. In Singles you can lean more on having the bulk to survive a hit and retaliate, or carrying a Focus Sash, or benefiting from Sturdy. Doubles makes all that unreliable: sure, you have the bulk to tank anything X Pokemon can take out, but you can't make any assumptions about what kind of partner it has, so that's not a hard-and-fast rule about being able to counter X in an actual match.
Hyper Voice is actually less common than you might think. There's a lot of good Special attackers that lack it, and a lot of the Pokemon that have Hyper Voice are kind of underwhelming as Special attackers, or underwhelming in some other way.
In terms of being a supporter, aside from Taunt shenanigans, I believe Cresselia might actually prefer Audinite. It gives it a decent supporting ability and great secondary typing. All you do is take your set, switch out the stones and replace Psychic with Moonblast.
Sablenite is superior for Trick Room, but as a general supporter Audinite is probably superior, particularly for stall teams, thanks to a useful added typing and the utility of Healer.
Regigigas would be insane with a lopunnite: base 220 attack and 130 speed combined with 110/120/110 defenses, scrappy Stab Return/Frustration+Drain Punch. If megaevolution negates slow start then it is even more stupid. I mean, I don't want to give you the wrong impression. I think it would be really cool to use but at the same time it would be toxic for the meta. The same could also be said about Slaking and for this purpose I am going to assume that mega evolution does negate the base form's ability.
Keep in mind Deoxys-Attack is legal in Doubles, and not even that
good. Of course, Regigigas has actual bulk, so it's a different situation, but just being hilariously fast and insanely hard-hitting isn't actually a dealbreaker for Doubles.
Slow Start is an effect that is applied when a Pokemon with Slow Start enters the battle. Regigigas will have to wait out the full Slow Start effect the first time it comes in and Mega Evolves, but wouldn't once it has Scrappy.
IIRC Truant checks if the Pokemon made a previous move while it had the Truant ability at the time the move is made in the turn order, so once Slaking mega evolves, Truant no longer checks its moves and affects its success.
In both cases the Ability going away means the Ability goes away. Slow Start's effect vanishes if Slow Start is replaced, instantly, and Truant only applies if, you know, you
have Truant. Otherwise Skill Swapping/Entrainmenting (Moxie from Pyroar is the popular choice) those two wouldn't be something people did in Doubles.
