Lovely team and I definitely support the use of banded flygon, it's one of my favourite sets to use in UU and it's on a lot of my teams ;) the team's solid already so most of my suggestions won't be vital but I see some things which could improve it anyway. uh let's go :>
Raikou 
Well the first thing I see is that you're using rash to have access to Aura Sphere, while I would sometimes support this it means that your Raikou speed ties with scarf Mienshao which is never good. Aura Sphere doesn't really cover a lot, it will do nothing to snorlax / porygon2 & tbh there's not much else a STAB thunderbolt won't take care of. Shadow Ball is also a really odd choice on him, you say it nails Bronzong and Chandelure on the switch, but nobody switches Chandy into Raikou ( outsped and 2hko'd by tbolt ) and Bronzong takes neutral from it anyway.
Something that should be there but isn't, however, is Volt Switch. Possibly one of the best moves in the game, especially for a Choice user, it lets you pivot around and scout for switchins which is great. Go with Shadow Ball -> Volt Switch, and Extrasensory should be used over Aura Sphere since it hits Roserade and the Nidos harder while letting you use a Timid nature.
Chandelure 
Cool set and very original, not sure how much it will work in practice and you say you want to change it so yeah. I'm gonna suggest a SubSplit set since you already have two potent Choicers.
Chandelure @ Life Orb
Trait: Flame Body
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid / Modest Nature
Substitute
Fire Blast
Shadow Ball
Pain Split
Obviously Snorlax still walls you, but it's not any worse than your previous set and at least behind a Substitute you can freely switch out from Pursuit, or even Pain Split to dent that massive HP stat. This set even takes advantage of residual damage from Life Orb, SR weakness, and Sub to abuse Pain Split easier. Flame Body might seem odd but I actually love using it now, lets you easily switch into random U-Turns and burn the fool :3 and one amazing thing about it is that Porygon2 no longer Traces your Flash Fire and walls you, so you can get surprise KOs. Your team isn't even weak to fire at all, so you won't be taking advantage of Flash Fire a lot. Fire Blast -> Flamethrower since you can usually afford to miss, but it's up to you I guess. The nature is based on preference, I don't really know which is better lol.
Flygon 
Looking good, the only thing I would suggest is Outrage > Fire Punch, your Chandelure and Snorlax cover Bronzong and EQ hits all other things harder so it's pretty redundant. Outrage is really freaking powerful and in a lot of situations superior to Dragon Claw.
Also, after using Banded Flygon a lot, I think you're okay to go with an Adamant nature. You still outspeed the main lower speed tier of like Heracross and stuff, but what's notable about Adamant is that it lets you 2hko standard Rhyperior with Outrage, who's a common switch in to the scarf set. Up to you I guess.
Gligar 
Sweet.
Mew 
Well it's okay I guess, but since your team obviously struggles with Honchkrow, Bisharp and other Sucker Punchers, I have a lovely replacement for him... Swords Dance Heracross :D
Heracross @ Leftovers 
Trait: Guts
EVs: 4 HP / 252 Atk / 252 Spd
Nature: Jolly
Swords Dance
Close Combat
Megahorn
Stone Edge
Swords Dance Heracross is a really underrated set, it has amazing power and can single handedly break down stall teams with the combination of its amazing STABs and Guts. It can even lategame sweep when threats that can revenge it have been removed ( Aerial Ace Mienshao ._. ). Most importantly it provides you with a solid Honchkrow check, it outspeeds naturally and KOs 99% of the time, 100% when SR is up, with Stone Edge. It can even take a +2 Sucker Punch if you somehow let it get that many boosts. Honestly it's just amazing, usual counters to the more common Scarf set, like Gligar, Cofagrigus etc can do nothing to it while it boosts up in their face and 2hko's them.
Snorlax 
I like it, but I've found that the CB set is too easy to set up on. For example, your opponent has SubCM Raikou out. You send in Snorlax since it's your only decent check, it hits you with Thunderbolt, you EQ and break its sub, it can then switch out to a flyer / levitator and force you out. With Leftovers, its damage output is still great, but the freedom to switch moves and the recovery at the end of each turn keeps it healthy and able to continuously come in and absorb special hits throughout the match. You can keep the same EV spread and moves obviously, but I've found Leftovers better in almost all situations.
Lol i'm done. That took a while -_- I tried to explain my thoughts thoroughly and whatever so sorry if I went on a bit :L a fun team to rate and I will definitely be stealing it lmao. Hope I helped.
