I'm going to answer this as if you are partaking in a standard tournament which isn't following "Tier" rulings.
*Your Blaziken is being posed as a mixed sweeper when its attack is much greater and you have no fear of burn so:
For starters Blaziken needs to have speed boost to really cause a problem as blaze only works if he can live the hits that take him down to that much HP.**
EVs should be spread mostly into attack (252) and speed (252) to make sure he is hitting as hard and first from the first turn and then the rest into defence
You should be looking at an Adamant nature to really boost his attack as well.*
Moveset has a few options but what I prefer is
Protect (To guarantee the SB)
BlazeKick for STAB and crit rate
Sky Uppercut for STAB and POA
Earthquake for other Firetypes
Secondly, Fly on latias is a no no. Fly in general in competitive is a free turn to switch/set up or hit a thunder which will do even more damage when you're in the air so its normally not recommended.
Its a good moveset however if you could get nature changed. Unless you're going however to hack the game or find someone with the right nature to trade with I would recommend modifying the moveset.
Run the unique item that latias/latios is holding that increases (spd and def) then
EV (252atk) and (252Spe) (4hp)
Waterfall is great for flinch and high BP
Roost helps for Reliable Recovery
Dragon Claw has STAB and high BP
Zen Headbutt has high BP and also chance to flinch.
Your serperior has the most competitive ability it has access to. You've got a puzzle you've almost completed with it by purely having that combined with leaf storm. The recommendation I have though is though is to give it a dragon fang/plate or anything to increase a dragon type move and run
Timid Serperior (252spa) (252spe) (4def)
Dragon Pulse is a very powerful attack after leafstorm + Dragon fang
Knock Off helps stop pokemon become more powerful/recover and stops some in their tracks
Taunt helps you stop being set up on
Leafstorm...ups your special attack because of contrary,
I love Plusles cute design but he gets outmatched by Emolga His typing stops ground type moves and his insane speed allows you to cripple in almost every scenario.
(Modest/Timid nature 252spa 252sp 4hp)
Electro Ball...The faster you are the more damage is does
Acrobatics...Don't Hold an item and it goes to BP 130
Thunder wave...Beefs up electro ball and you might get a free turn
Pursuit...For when they try to switch into a counter
Azumarill gives me happy thoughts...Mine is named Susan and a few of my friends have a joke "When Susan comes in, everything switches out"...To an extent its true however, I have neglected her a little because she keeps getting outmatched.
She's a sweeper, and a wall, and an annoyance...But people now expect her moveset. Your team is very powerful, it hits hard and fast by the looks of things but you're missing an element every team needs despite what people say.
My Favourite Wall is Either Clefable or Blissey...I Don't run a Clefable so I can't give my opinion but Blissey is a horror...With a Bold Nature Increase that defence as much as you can as its pretty appalling.
The Ev (252DeF 252Spd and 4HP)
In a battle spot game this set single handily won against a Primal Groudon/Primal Kyogue and Darkrai.
Set up a turn of toxic and just stall them out occasionally hitting the seismic toss to make life easier.
You could always run a rocky helmet thinking about it to make up for the poor defence.
Now I've tried to keep to the pokemon in your team because clearly you have a bond with them. But occasionally its just not possible to so I do apologise about suggesting to remove some such as Azumarill, Plusle and finally Hariyama.
If you weren't going to tournament level I'd personally keep them. They're a fun pokemon to run but not necessarily the best.
As I was saying, the final replacement...Hariyama. I like him, bulky and packs a punch.
However, replace him with Guts conkledurr. When people see a Physical attacking pokemon they will-o-wisp cutting your attack.
Will-o-wisp conkledurr and all that's happening is gradual damage.
Have an Adamant Nature (252AtkEV and 125Spd 125def with the rest in HP)
You can hit with powerful moves like stone edge, Superpower, Earthquake etc its a pokemon you can really make for coverage or serve as a purpose
All in all these are just opinionated reviews from experience so don't take on board everything...these are just suggestions. At THIS point in time your team wouldn't stand up very well in tournament due to the attacks you've got (Which are clearly play through sets)
You just need to find a strategy you're comfortable with and make it your own :)
Feel free to add my friend code and I can help trade you pokemon*