OK I'm sick and I'm attempting my second answer now after my browser randomly linked me to a shopping site about Chickens, don't know why that happened -__- so I'm sorry if this is a bit sloppy but ill try answer to the best of my abilities.
Aerodactyl
Not fitting it really you already have a spinner and most leads are weather leads who have no problem taking this Pokemon out.
You want a Stealth Rock abuser who can last the duration of the game.
Swampert (M) @ Leftovers
Trait: Torrent
EVs: 208 HP / 252 Atk / 48 Spd
Adamant Nature (+Atk, -SAtk)
- Earthquake
- Superpower
- Stealth Rock
- Ice Punch
He has the ability to stay for the duration of the game and deal nice damage/coverage and lay rocks out.
His only problem in sun is opposing sun teams really as most sun teams carry at least one chlorophyll abuser.
Hippowdon (M) @ Leftovers
Trait: Sand Force
EVs: 252 HP / 52 Atk / 204 SDef
Adamant Nature (+Atk, -SAtk)
- Ice Fang
- Slack Off
- Earthquake
- Stealth Rock
Yes this is Hippowdon in sun.
it can function well in any weather and is a good asset with Sand force making sand teams less of a threat.
It can set up rocks and hit rather hard as well as sponge attacks for the team.
Sdef investment is to help it take water attacks and Hp Ice better.
Slack Off is something Swampert lacks.
The choice is up to you really, personally I would choose Swampert but that's biased seen as Swampert is one of my favorite Pokemon.
They both have very similar roles and stats so try them both out.
Breloom
Smogon hasn't updated the Breloom page in a while, you do realize technician is now available?
A Technician set will benefit your team better as you mentioned you are struggling to take out bulky Pokemon.
A Technician set cause sheer Destruction.
Breloom (F) @ Life Orb
Trait: Technician
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Bullet Seed
- Mach Punch
- Swords Dance
- Spore
Defintly try this set, a Bullet Seeds minimum Power after technician is 75 close to Seed Bombs 80.
It has a good chance to hit multiple times as well as having a small chance to crit on each bullet.
Jolly is chosen over Adamant in this situation because of Gliscor running 72 speed to out speed the base 70 Pokemon.
It also lets you outs peed Adamant Dragonite and break its Multiscale before hitting multiple other times.
Swords dance is the icing on the cake really, you can sweep entire teams with this set.
But I do understand why you would want to keep your previous set, or at least a similar variation seen as my set is full out attack.
Breloom (F) @ Toxic Orb
Trait: Poison Heal
EVs: 236 HP / 212 SDef / 60 Spd
Careful Nature (+SDef, -SAtk)
- Seed Bomb
- Bulk Up
- Drain Punch
- Spore
This set is similar to yours but is more balanced on the defenses.
Mach Punch isn't a good idea because it has no boost just stab, so you would need a boosting move to preform a sweep.
Ninetails
I don't like Focus Sash though Ninetails isn't the most bulky it needs the offence to pull off the set you are trying to do.
Try this set it has good coverage and will hit anything hard.
Ninetales (M) @ Life Orb/Leftovers
Trait: Drought
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature (+SAtk, -Atk)
- Overheat
- Energy Ball
- Hidden Power [Fighting]
- Flamethrower
I would personally use Life Orb but then you would need to be extra careful at keeping Starmie up.
Leftovers is a valid option though, the only problem is that it doesn't hit hard enough.
Hidden Power Fighting is coverage against Tyranitar and Heatran on the switch in.
Though it isn't a OHKO on either of them but you can switch out and leave them on low health.
Energy Ball is over Solar Beam due to the fact Politoed is a common counter to Ninetails and you don't want to be locked into Solar Beam when Polioeds up with rain.
Starmie
Starmie is fine though Ice Beam is needed, your currently struggling with Grass users which are usually chlorophyll users in Ou, You need to hit them hard on the switch ins.
You may also want to keep Hp fire to counter Gensect and Scizors but psychic is the only good replacement.
Arcanine
Personally I think Arcanine sucks in UU let alone OU.
There are much better Pokemon out there you should defiantly try out.
Unfortunately they don't fit into the team
Your best bet is to use Scizor
Scizor (M) @ Choice Band
Trait: Technician
EVs: 180 HP / 252 Atk / 76 Spd
Adamant Nature (+Atk, -SAtk)
- Bullet Punch
- U-turn
- Pursuit
- Superpower
Fits in perfect and is great paired with Brelooms Mach Punch.
Bullet Punch with a Choice Band will help you take out Pokemon like Venasur and Thundurus Better even if they resist it.
Swords dance is probably the better choice here but I had the Cband set loaded up on Po already so who cares :D.
Salamance
He fits in very well here, but I am going to suggest Garchomp for the reason that Thundurus Out speeds it.
Garchomp beats both Salamance and Thundurus.
The change is defiantly not needed but would be a good idea.
Garchomp (F) @ Choice Scarf
Trait: Rough Skin
EVs: 252 Atk / 252 Spd
Naive Nature (+Spd, -SDef)
- Stone Edge
- Fire Fang/Fire Blast
- Outrage
- Earthquake
Garchomp helps you counter Jirachi much better avoiding Thunder, being able to Equake it and the fact Iron Head wont touch Garchomp and even if it does its at the expense of the Jirachis Health thanks to Rough Skin.
It out speeds Modest scarf Latios, all in all Garchomp is probably the better choice though you will miss out on Moxie.
Finally I'm finished I hope this helps and good luck in testing.