If you can't get Aromatherapy on Blissey, go with Heal Bell. You can get Heal Bell by breeding with Skitty (pretty much the only thing Skitty is good for).
On Metagross, I'd drop Aerial Ace. It doesn't hit anything noteworthy that Metagross has trouble with and has a rather low base power. A neutral Meteor Mash hits harder than a super effective Aerial Ace. Go with Agility or Rock Slide. After Agility Metagross outruns the majority of the frontier, and if you also get the attack boost from Meteor Mash Metagross becomes fairly unstoppable, while Rock Slide is situational but hits Gyarados and Zapdos for super effective damage.
Ice beam is a bit redundant on Latios. Flying types are hit by Thunderbolt, Grass types don't scare a dragon, and with levitate you shouldn't fear grounds too much whilst Dragon Claw also hits dragons. Latios generally runs best with either a full sweeper moveset or Calm-Mind-Recover.
Psychic is mostly neutral STAB coverage, but it gets notable OHKO's on Gengar and Heracross, two pokémon that can cause trouble with Ice Punch and Megahorn respectively. Dragon Claw is secondary STAB that hits opposing Latios/Latias, and other dragons hard. Thunderbolt and Surf provide additional coverage, Thunderbolt being useful to hit water types that frequently carry Ice Beam and Surf getting useful hits on pokémon like Aggron and Steelix, although Surf can be replaced by Calm Mind or Recover.
-Thunderbolt / Dragon Claw
CM-Recover is a way to get around pokémon like Blissey that can recover repeated hits, and it can be used to build up against a non-threatening foe. It also allows you to get around Mirror coat users like Swampert and Wobbuffet.
Tyranitar works best as a Dragon Dance sweeper in my opinion. The AI is generally stupid enough to let you set up at least one Dance, and after DD Tyranitar is almost unstoppable. It requires breeding from a dragon through Charizard, but it's worth it.
-Crunch / Aerial ace
I've never used mixed Salamence, but I guess it works. Alternatively you can go with special Salamence (Dragon Claw / Fire Blast / Hydro Pump / Crunch) or DD-mence (Dragon Dance / Aerial Ace / Earthquake / Rock Slide).
Dragonite is in 3rd gen a bit like a lesser Salamence. Less speed, less offensive stats, and no Intimidate. Although it has better defensive stats, it lacks a recovery move and is not nearly as defensively capable as pokémon like Suicune. Apart from Thunderbolt Salamence does everything better.
Blaziken isn't really worth using at this level in the Frontier. It lacks imporant speed to make up for its fragility. Although it has decent offensive stats, it's too slow to take full advantage of them, and unlike Metagross, it can't take repeated hits reliably while attacking.
Master balls are the cheapest thing ever invented. It's more fun catching everything with balls that can fail. 'caught Latios in the wild without master ball ftw'